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Tangent graph | Graphs of trig functions | Trigonometry | Khan Academy

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This 120-second clip introduces the graph of y=tan⁡θy=\tan\theta by first building a unit-circle interpretation of tangent. On the left, the instructor draws axes, a unit circle, and a terminal ray for an angle θ\theta, labels the intersection point as (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta), and writes the identity tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}. He then explains that this same ratio is the slope of the ray, ΔyΔx\frac{\Delta y}{\Delta x}, giving a geometric way to understand tangent values. The right half of the screen already contains a large radian-labeled coordinate grid reserved for the eventual graph, but no tangent curve is plotted in this segment. The clip ends as the instructor cleans up the diagram and begins a table for different angles. This 120-second whiteboard segment introduces graphing y=tan⁡θy = \tan θ by first building a small table of values from the unit circle. The presenter interprets tangent as the slope of the terminal ray, computes tan⁡0=0\tan 0 = 0, explains tan⁡(π/4)=1\tan (π/4)=1 using equal coordinates and the identity sin⁡θ/cos⁡θ\sin θ / \cos θ, and records tan⁡(−π/4)=−1\tan (-π/4)=-1. The right-hand coordinate grid remains blank during this excerpt. This 120-second whiteboard segment derives tan⁡(−π/4)=−1\tan(-\pi/4)=-1 from unit-circle coordinates, fills a small table of tangent values, plots the first three points of y=tan⁡θy=\tan\theta, and then explains why the graph is not a line by showing that tan⁡θ\tan\theta grows without bound as θ→π/2−\theta\to\pi/2^{-}, culminating in a dashed vertical asymptote at θ=π/2\theta=\pi/2. This 120-second whiteboard excerpt teaches the graph of y=tan⁡θy = \tan θ by linking the unit-circle slope of a ray to the shape of the tangent curve. The instructor first completes the central branch between the vertical asymptotes at θ=−π/2θ = -π/2 and θ=π/2θ = π/2, explaining that the slope tends to +∞\infty near π/2π/2 from the left and to -∞ near -π/2 from the right. He then continues past π/2π/2, showing that immediately after crossing the asymptote the ray’s slope is hugely negative, so the graph jumps to a new branch below the axis and rises again. Near the end, he introduces the example angle 3π/43π/4 and begins rewriting it as π/2+π/4π/2 + π/4, but the clip stops before the example is fully worked out. This 119-second whiteboard segment explains y=tan⁡θy = \tan θ by treating tangent values as slopes of terminal rays on the unit circle. The speaker derives tan⁡(3π/4)=−1\tan (3π/4) = -1 from a second-quadrant 45-45-90 triangle, then moves to tan⁡(π)=0\tan (π) = 0 and the next positive unit slope, plots corresponding points on the θ-y graph, and uses the unbounded behavior near 3π/23π/2 to draw vertical asymptotes and state that the tangent graph repeats every π radians. This video segment introduces the graph of the tangent function, y=tan⁡θy = \tan \theta. It visually presents the characteristic repeating branches separated by vertical asymptotes. The narrator explains that the function is periodic, meaning the graph pattern continues indefinitely in both directions along the horizontal axis.

Use the learning inspector for key ideas and moments, or open the reading tabs for the complete notes.

Chapters

0:00Introduce the goal: graph of y=tan⁡θy=\tan\theta0:10Draw a unit circle for visualization0:35Represent angle θ\theta in standard position0:46Label the unit-circle point (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta)1:05State tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}1:25Interpret tangent as slope ΔyΔx\frac{\Delta y}{\Delta x}1:43Begin transitioning to a table of values2:00Setup: table, unit circle, and blank graph2:03Evaluating tan 0 from a horizontal ray2:13Choosing easy angles to infer the graph shape2:27Deriving tan⁡(π/4)=1\tan (π/4)=1 from equal coordinates3:25Introducing tan⁡(−π/4)=−1\tan (-π/4)=-14:00Unit-circle coordinates for −π/4-\pi/44:18Computing tan⁡(−π/4)\tan(-\pi/4) as sine over cosine4:31Cleaning the unit circle and completing the table4:46Setting up the θ\theta-yy graph4:58Plotting (0,0)(0,0), (π/4,1)(\pi/4,1), and (−π/4,−1)(-\pi/4,-1)5:12Why the tangent graph is not a line5:19Behavior as θ→π/2−\theta\to\pi/2^{-}5:53Drawing the vertical asymptote at θ=π/2\theta=\pi/26:00Setup: tangent graph, table, and unit circle6:13Slope behavior near ±π/2π/2 and the central branch6:38Vertical asymptote and completion of the principal branch6:50Continuing past π/2π/2: why the next branch starts below7:33Introducing 3π/43π/4 as the next example angle8:00Identifying 3π/43π/4 on the unit circle8:17Using a 45-45-90 triangle to get slope -18:40Moving from 3π/43π/4 to π and the next π/4π/4 increment9:04Approaching 3π/23π/2 and positive infinity9:20Sketching the tangent branch and repeating every π radians9:51Drawing asymptotes and summarizing the graph10:00Introduction to the Tangent Graph10:07Periodicity of the Function

Learning script

Generated from the video's visuals and explanation; not verbatim speech.

The clip opens with the function name y=tan⁡θy=\tan\theta written at the upper left while a large empty coordinate grid waits on the right. The immediate question is how to understand the tangent graph before actually plotting it.

To answer that, the instructor builds a small unit-circle diagram on the left: teal axes and a circle centered at the origin. This auxiliary picture is not the final graph; it is a geometric device for reading off tangent values from angles.

Next, a yellow ray is drawn from the origin into the first quadrant, and the angle between the positive xx-axis and the ray is labeled θ\theta. This places the angle in standard position so its terminal side can meet the circle at a definite point.

The intersection point is then labeled (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta). The key detail is the coordinate assignment: the horizontal coordinate is cosine and the vertical coordinate is sine. The speaker even audibly corrects an initial slip, reinforcing that the point is not (sin⁡θ,cos⁡θ)(\sin\theta,\cos\theta).

With the point identified, the lesson writes the quotient identity tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}. In this unit-circle setting, that means tangent is the ratio of the point’s yy-coordinate to its xx-coordinate.

The instructor then adds the slope interpretation ΔyΔx\frac{\Delta y}{\Delta x}. Because the ray starts at the origin and passes through (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta), the rise-over-run of that ray is exactly the same ratio as sin⁡θcos⁡θ\frac{\sin\theta}{\cos\theta}. This is the central conceptual bridge of the clip: tangent can be seen as a slope, not merely as an algebraic fraction.

Finally, the extra annotations are cleared away and a new vertical line is drawn at the far left as the start of a table. The spoken transition indicates that the next stage will list several angles θ\theta and compute the corresponding tangent values, but the table itself is not filled in before the clip ends.

The clip opens on a three-part whiteboard layout: a handwritten title y=tan⁡θy=\tan\theta, a two-column table headed θ\theta and tan⁡θ\tan\theta, a unit circle in the middle, and a blank Cartesian grid on the right. The purpose is to prepare for graphing the tangent function by first collecting a few reliable values.

The presenter starts with the easiest input, θ=0\theta=0. On the unit circle the corresponding ray lies along the positive xx-axis, so there is no vertical change as the horizontal coordinate changes. Using the slope interpretation of tangent, this gives tan⁡0=0\tan 0=0, and the pair (0,0)(0,0) is written into the table.

Next, the speaker explains the selection strategy: choose angles whose tangent values are easy to recognize, because those sample points will help reveal the overall shape of the graph of y=tan⁡θy=\tan\theta. This connects the geometric unit-circle reasoning to the numerical table that will later be transferred to the coordinate grid.

The next example is θ=π4\theta=\frac{\pi}{4}, described aloud as a 45-degree angle. A ray is drawn into the first quadrant, and a small right triangle is sketched to emphasize that the horizontal and vertical changes are equal. Since the slope is rise over run, equal changes imply slope 11, so tan⁡(π4)=1\tan\left(\frac{\pi}{4}\right)=1.

The presenter reinforces the same conclusion algebraically by invoking tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}. At θ=π4\theta=\frac{\pi}{4}, the sine and cosine values are the same, so their quotient is 11. The table is then updated with the row (π4,1)\left(\frac{\pi}{4},1\right).

Finally, the speaker introduces θ=−π4\theta=-\frac{\pi}{4} and draws the corresponding ray below the positive xx-axis in the fourth quadrant. The written table entry records tan⁡(−π4)=−1\tan\left(-\frac{\pi}{4}\right)=-1. The visual setup suggests a negative slope because the ray moves downward while progressing to the right, although the spoken explanation is cut off before it is fully completed.

The clip opens on a unit circle with the angle −π/4-\pi/4 marked and a table for y=tan⁡θy=\tan\theta already listing 0↦00\mapsto 0 and π/4↦1\pi/4\mapsto 1. The speaker identifies the relevant point on the circle: its cosine, the xx-coordinate, is 22\frac{\sqrt2}{2}, while its sine, the yy-coordinate, is −22-\frac{\sqrt2}{2}. This establishes the coordinate inputs needed for the tangent calculation.

Using the definition tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}, the video substitutes those two coordinates and obtains tan⁡(−π/4)=−1\tan(-\pi/4)=-1. The reasoning is that the magnitudes are equal but the signs are opposite, so the quotient is −1-1. By the end of this step, the missing table entry for −π/4-\pi/4 is filled with −1-1.

Before moving to the graph, the presenter erases auxiliary construction marks from the unit circle so the same diagram can be reused. This cleanup does not change any values; it only prepares the board for the next stage, where numerical tangent values will be transferred onto a coordinate grid.

The right-hand grid is introduced as the graph of y=tan⁡θy=\tan\theta, with the horizontal axis labeled θ\theta and the vertical axis labeled yy. The speaker then plots the first three known points directly from the table: (0,0)(0,0), (π/4,1)(\pi/4,1), and (−π/4,−1)(-\pi/4,-1). These points anchor the beginning of the tangent curve.

Immediately after plotting them, the video warns against concluding that the graph is a straight line. The three points may look collinear at this coarse stage, but the speaker shifts attention to what happens as the angle increases toward π/2\pi/2. On the unit circle, the terminal ray becomes more and more vertical, so its slope becomes larger and larger positive.

At θ=π/2\theta=\pi/2 itself, the slope is undefined, but the limiting behavior as θ→π/2−\theta\to\pi/2^{-} is that tan⁡θ\tan\theta approaches +∞+\infty. To represent this on the graph, a dashed vertical line is drawn at θ=π/2\theta=\pi/2, identifying a vertical asymptote of the tangent function.

The screen is organized as a teaching board for y=tan⁡θy = \tan θ: on the left are a handwritten title, a small θ/tan⁡θθ / \tan θ table, and a cyan unit circle with yellow rays; on the right is a coordinate plane with horizontal axis θ and vertical axis y. This layout prepares a translation from geometric angle information to a function graph.

The instructor explains the central branch by tracking the slope of the ray on the unit circle. As the angle approaches π/2π/2 from below, the ray becomes steeper and steeper in the positive direction, so the tangent value grows without bound; visually, the red curve rises toward the dashed line at θ=π/2θ = π/2.

He then asks what happens as the angle approaches -π/2. In the same slope picture, the ray becomes steeply negative, so the tangent value tends to -∞. On the graph, the left end of the branch drops toward the dashed line at θ=−π/2θ = -π/2.

At the boundary angle, the speaker states that the function is “not quite defined” and identifies a vertical asymptote. This turns the verbal limiting behavior into a clear graphical feature: the principal branch of tangent is trapped between two vertical asymptotes and passes through the origin.

Having finished the section over this part of the θ-axis, the instructor says the graph can keep going. The key move is to consider an angle just after crossing π/2π/2 rather than stopping at the asymptote.

For an angle slightly larger than π/2π/2, the corresponding ray lies in the second quadrant. Its slope is therefore negative and very large in magnitude. This explains why the graph does not continue upward through the asymptote; instead it jumps to a new branch far below the x-axis just to the right of π/2π/2.

As θ increases further in that new interval, the slope becomes less and less negative, so the fresh branch rises. The visual logic is that each new period of tangent repeats the same pattern: unbounded growth near one asymptote, discontinuous reset, then renewed increase.

To anchor the next interval with a concrete example, the instructor marks an angle in the second quadrant and names it 3π/43π/4. He begins justifying the choice by rewriting it as 3π/4=π/2+π/43π/4 = π/2 + π/4, indicating that this angle lies a quarter-turn past the asymptote.

The clip ends while this example is still being set up. The mathematical point established so far is not a final numerical value for tan⁡(3π/4)\tan (3π/4), but the method: use the unit-circle slope just beyond π/2π/2 to explain why the tangent graph restarts on a lower branch and then increases.

The clip opens with the instructor locating 3π4\frac{3\pi}{4} on the unit circle by rewriting π2\frac{\pi}{2} as 2π4\frac{2\pi}{4} and adding another π4\frac{\pi}{4}. The visible whiteboard links three representations at once: a table of θ\theta and tan⁡θ\tan\theta, a unit circle with yellow terminal rays, and a gridded graph of y=tan⁡θy=\tan\theta.

He then explains why this angle matters geometrically. The terminal ray forms another 4545-4545-9090 triangle, so the horizontal and vertical distances have equal magnitude. Because the ray lies in the second quadrant, the x-distance is negative and the y-distance is positive. Under the clip’s slope interpretation of tangent, that sign pattern gives tan⁡(3π4)=−1\tan\left(\frac{3\pi}{4}\right)=-1, matching the earlier slope seen at −π4-\frac{\pi}{4}.

Next the angle is increased to π\pi. At that position the terminal ray is horizontal, so the slope returns to 00, giving tan⁡(π)=0\tan(\pi)=0. Increasing by another π4\frac{\pi}{4} reaches the next special angle, visually consistent with 5π4\frac{5\pi}{4}, where the slope becomes positive 11 again. These values are translated into plotted points on the right-hand graph.

The discussion then turns to what happens as the angle approaches 3π2\frac{3\pi}{2}. The speaker emphasizes that the slope becomes more and more positive and approaches positive infinity. In his words, a small movement in the x-direction corresponds to a very large movement upward in the y-direction, which is why the curve steepens dramatically near that boundary.

Using those behaviors, he sketches the tangent branch on the graph. The curve rises through the plotted points and shoots upward beside the vertical line at 3π2\frac{3\pi}{2}. He then states that the same pattern repeats every π\pi radians, so the graph continues in identical branches across neighboring intervals of length π\pi.

Finally, he draws dashed vertical asymptotes at the odd multiples of π2\frac{\pi}{2} and uses them to separate the repeated branches. The closing visual message is that the graph of tangent is built from unit-circle slope values, has vertical asymptotes where the function becomes unbounded, and repeats periodically with period π\pi.

The video displays the equation y=tan⁡θy = \tan \theta alongside a unit circle diagram and a table of specific values. On the right, a coordinate plane shows the graph of the tangent function. The graph consists of multiple curved branches that pass through the origin (0,0)(0,0) and extend upwards and downwards towards infinity.

The narrator points out that the function is periodic. This means the pattern of the branches repeats at regular intervals. The graph shows these branches continuing infinitely to the left and right, separated by vertical dashed lines which represent asymptotes where the function is undefined.

Knowledge cards

01

Goal of the segment: understand the tangent graph

The clip introduces the problem of becoming familiar with the graph of y=tan⁡θy=\tan\theta. Instead of plotting immediately, it first explains a geometric interpretation using the unit circle. The large right-hand grid is prepared for later graphing, but no curve is drawn in this excerpt.

y=tan⁡θy = \tan \theta
02

Unit circle as a visualization tool

A small coordinate system and circle are drawn on the left to represent the unit circle. This construction lets an angle θ\theta be converted into a point in the plane, which then supports the definitions of sine, cosine, and tangent used in the rest of the clip.

03

Angle in standard position

The angle θ\theta is shown with one side on the positive xx-axis and the other side as a ray from the origin. That ray intersects the unit circle, linking angle measure to a specific coordinate point.

04

Unit-circle point coordinates

The intersection of the terminal ray with the unit circle is labeled (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta). The clip explicitly corrects the common swap error: the xx-coordinate is cosine and the yy-coordinate is sine.

(cos⁡θ, sin⁡θ)(\cos\theta,\ \sin\theta)
05

Tangent quotient identity

The instructor states and writes tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}. Within the unit-circle picture, this is the ratio of the point’s vertical coordinate to its horizontal coordinate. The clip does not explicitly mention the usual restriction cos⁡θ≠0\cos\theta\neq 0.

tan⁡θ=sin⁡θcos⁡θ\tan\theta = \frac{\sin\theta}{\cos\theta}
06

Tangent as slope of the terminal ray

Because the ray begins at the origin and passes through (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta), the same ratio can be read as slope: change in yy over change in xx. This gives a direct geometric way to understand the magnitude and sign of tangent values as the angle changes.

tan⁡θ=ΔyΔx=sin⁡θcos⁡θ\tan\theta = \frac{\Delta y}{\Delta x} = \frac{\sin\theta}{\cos\theta}
07

Transition to tabulating values

After establishing the geometric meaning of tangent, the instructor cleans up the diagram and begins a table at the far left. The intended next step is to compare several angles θ\theta with their tangent values, but the table entries are not shown within this 120-second clip.

08

Tangent as slope on the unit circle

This segment defines the working interpretation used throughout: for an angle θ\theta, tan⁡θ\tan\theta is read as the slope of the terminal ray drawn from the origin of the unit circle. A horizontal ray gives slope 0, an upward 45-degree ray gives slope 1, and a downward 45-degree ray gives slope -1.

tan⁡θ=slope of the terminal ray\tan\theta = \text{slope of the terminal ray}
09

Why tan⁡0=0\tan 0 = 0

When θ=0\theta=0, the ray lies exactly along the positive xx-axis. As xx changes, yy does not change at all, so the slope is 0. The video records this as the first table entry.

tan⁡0=0\tan 0 = 0
10

Strategy for sketching y=tan⁡θy = \tan θ

Before drawing the full graph, the presenter chooses a few angles with especially simple tangent values. These sample points are entered into a table of θ\theta versus tan⁡θ\tan\theta and are intended to help infer the shape of the graph on the blank coordinate grid.

11

Why tan⁡(π/4)=1\tan (π/4) = 1

At θ=π4\theta=\frac{\pi}{4}, the unit-circle point has equal xx- and yy-coordinates. Moving the same amount horizontally and vertically means rise equals run, so the slope is 1. The presenter also notes that this corresponds to a 45-degree angle.

tan⁡(π4)=1\tan\left(\frac{\pi}{4}\right)=1
12

Using sin⁡θ/cos⁡θ\sin θ / \cos θ to confirm tangent

The video states the identity tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta} and applies it at θ=π4\theta=\frac{\pi}{4}. Because sine and cosine are equal there, their quotient is 1, matching the geometric slope argument.

tan⁡θ=sin⁡θcos⁡θ\tan\theta = \frac{\sin\theta}{\cos\theta}
13

Table entry for -π/4

The presenter then considers θ=−π4\theta=-\frac{\pi}{4} and draws the ray into the fourth quadrant. The table explicitly records the value −1-1, consistent with a downward-sloping ray of the same steepness as the π4\frac{\pi}{4} case. The spoken justification begins but the clip ends before it is fully finished.

tan⁡(−π4)=−1\tan\left(-\frac{\pi}{4}\right)=-1
14

Unit-circle coordinates for −π/4-\pi/4

For the angle −π/4-\pi/4 shown on the unit circle, the cosine is the xx-coordinate 22\frac{\sqrt2}{2} and the sine is the yy-coordinate −22-\frac{\sqrt2}{2}. The video uses these exact coordinates as the starting data for computing tangent.

cos⁡(−π4)=22,sin⁡(−π4)=−22\cos\left(-\frac{\pi}{4}\right)=\frac{\sqrt{2}}{2},\quad \sin\left(-\frac{\pi}{4}\right)=-\frac{\sqrt{2}}{2}
15

Tangent as sine over cosine

The tangent of an angle is computed as the ratio of sine to cosine. In this clip, that definition is applied to the unit-circle coordinates to turn geometric information into a function value.

tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}
16

Value of tan⁡(−π/4)\tan(-\pi/4)

Substituting the coordinates for −π/4-\pi/4 gives a quotient of −1-1. This value is then written into the table as the entry corresponding to θ=−π/4\theta=-\pi/4.

tan⁡(−π4)=−1\tan\left(-\frac{\pi}{4}\right)=-1
17

Starting the graph of y=tan⁡θy=\tan\theta

The graph is set up with horizontal axis θ\theta and vertical axis yy. The first plotted points come directly from the table: (0,0)(0,0), (π/4,1)(\pi/4,1), and (−π/4,−1)(-\pi/4,-1).

(0,0),(π4,1),(−π4,−1)(0,0),\quad \left(\frac{\pi}{4},1\right),\quad \left(-\frac{\pi}{4},-1\right)
18

Tangent is not a straight line

Even though the initial plotted points may suggest linear behavior, the video explicitly says the graph is not a line. The next step examines limiting behavior rather than connecting the points as if they determined a line.

19

Growth as θ→π/2−\theta\to\pi/2^{-}

As the angle approaches π/2\pi/2 from below, the terminal ray on the unit circle becomes nearly vertical, so its slope becomes arbitrarily large positive. This is the intuitive basis for unbounded growth of tangent near π/2\pi/2.

θ→π2−  ⟹  tan⁡θ→+∞\theta\to\frac{\pi}{2}^{-}\implies \tan\theta\to +\infty
20

Vertical asymptote at θ=π/2\theta=\pi/2

Because tan⁡θ\tan\theta becomes undefined at π/2\pi/2 and tends to infinity on approach, the graph is marked with a dashed vertical asymptote at θ=π/2\theta=\pi/2.

θ=π2\theta=\frac{\pi}{2}
21

Central branch of y=tan⁡θy = \tan θ

Between θ=−π/2θ = -π/2 and θ=π/2θ = π/2, the graph is drawn as one increasing branch through the origin. The instructor obtains this shape from the unit-circle slope picture: near π/2π/2 the slope becomes unbounded positive, and near -π/2 it becomes unbounded negative.

y=tan⁡θy=\tan\theta
22

Vertical asymptotes at ±π/2π/2

The clip explicitly says the function is “not quite defined” at the boundary and marks those locations with vertical dashed lines. These asymptotes separate one branch of the tangent graph from the next.

23

tan θ as slope of a ray on the unit circle

The lesson repeatedly interprets tan θ as the slope of the ray making angle θ with the positive x-axis. Steeper positive rays give larger positive tangent values; steep negative rays give large negative tangent values.

24

Why the graph jumps down just after π/2π/2

Immediately after crossing π/2π/2, the ray enters the second quadrant, where its slope is negative and very large in magnitude. Therefore the tangent graph does not continue upward through the asymptote; it restarts on a new branch below the x-axis and then rises as θ increases.

Detailed learning notes

Explore conditions, steps and evidence. Supplementary explanations are labeled separately from content shown in the video.

Symbols · 44

y=tan⁡θy = \tan \theta

Clear evidence
Shown in the video
Evidence
  1. Formula
    Observation

    At the upper left, the handwritten title/function label is y=tan⁡θy = \tan \theta.

  2. Audio
    Observation

    The speaker says he wants to get familiarity with the graph of tangent of theta.

Symbol

y=tan⁡θy = \tan \theta

Meaning

The dependent variable yy is the value of the tangent function at angle θ\theta; this is the function whose graph is being introduced.

Domain

θ\theta is an angle in radians on the coordinate grid; yy is real where tan⁡θ\tan\theta is defined.

xx-axis

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says, "So let's say that's a y-axis. This is my x-axis."

  2. Diagram
    Observation

    A teal vertical axis and horizontal axis are drawn on the left side as a unit-circle coordinate system.

Symbol

xx-axis

Meaning

Horizontal axis of the auxiliary unit-circle diagram; it also corresponds to the positive initial side of the angle θ\theta.

Domain

Real line in the auxiliary diagram.

yy-axis

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker identifies the vertical line as the y-axis while drawing the unit circle setup.

  2. Diagram
    Observation

    A teal vertical axis is drawn on the left side.

Symbol

yy-axis

Meaning

Vertical axis of the auxiliary unit-circle diagram; it supplies the sine coordinate of the point on the circle.

Domain

Real line in the auxiliary diagram.

θ\theta

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says, "if I have an angle, an angle theta, where one side is the positive x-axis".

  2. Diagram
    Observation

    A yellow ray from the origin forms an angle with the positive xx-axis, and the angle is marked θ\theta.

Symbol

θ\theta

Meaning

An angle measured from the positive xx-axis to a ray intersecting the unit circle.

Domain

Angles in radians; in this clip the drawn example lies in the first quadrant.

cos⁡θ\cos\theta

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker corrects himself and says the xx coordinate is the cosine of theta.

  2. Formula
    Observation

    The point on the circle is labeled (cos⁡θ,sin⁡θ)(\cos\theta, \sin\theta).

Symbol

cos⁡θ\cos\theta

Meaning

The xx-coordinate of the intersection point of the terminal ray with the unit circle.

Domain

For the unit circle, −1≤cos⁡θ≤1-1 \le \cos\theta \le 1; here it is shown as the horizontal leg of the right triangle.

sin⁡θ\sin\theta

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says the yy coordinate there is the sine of theta.

  2. Formula
    Observation

    The point on the circle is labeled (cos⁡θ,sin⁡θ)(\cos\theta, \sin\theta).

Symbol

sin⁡θ\sin\theta

Meaning

The yy-coordinate of the intersection point of the terminal ray with the unit circle.

Domain

For the unit circle, −1≤sin⁡θ≤1-1 \le \sin\theta \le 1; here it is shown as the vertical leg of the right triangle.

tan⁡θ=sin⁡θcos⁡θ\tan\theta = \frac{\sin\theta}{\cos\theta}

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says, "we know that tangent of theta is the same thing as the sine of theta over the cosine of theta."

  2. Formula
    Observation

    The handwritten equation tan⁡θ=sin⁡θcos⁡θ\tan\theta = \frac{\sin\theta}{\cos\theta} appears below the title.

Symbol

tan⁡θ=sin⁡θcos⁡θ\tan\theta = \frac{\sin\theta}{\cos\theta}

Meaning

Tangent is defined as sine divided by cosine, equivalently the ratio of the point’s yy-coordinate to its xx-coordinate on the unit circle.

Domain

Valid when cos⁡θ≠0\cos\theta \neq 0; the clip does not explicitly state the excluded angles.

Δy\Delta y

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says this is going to be your change in y.

  2. Formula
    Observation

    The handwritten slope expression includes Δy\Delta y in the numerator.

Symbol

Δy\Delta y

Meaning

Change in the vertical coordinate from the origin to the point on the unit circle; in this setup it equals sin⁡θ\sin\theta.

Domain

Shown for the drawn first-quadrant ray; generally a vertical displacement.

Δx\Delta x

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says this is over change in x.

  2. Formula
    Observation

    The handwritten slope expression includes Δx\Delta x in the denominator.

Symbol

Δx\Delta x

Meaning

Change in the horizontal coordinate from the origin to the point on the unit circle; in this setup it equals cos⁡θ\cos\theta.

Domain

Shown for the drawn first-quadrant ray; generally a horizontal displacement.

(cos⁡θ,sin⁡θ)(\cos\theta, \sin\theta)

Clear evidence
Shown in the video
Evidence
  1. Formula
    Observation

    The intersection point is labeled (cos⁡θ,sin⁡θ)(\cos\theta, \sin\theta).

  2. Audio
    Observation

    The speaker states that where the ray intersects the unit circle, the coordinates are cosine theta comma sine theta.

Symbol

(cos⁡θ,sin⁡θ)(\cos\theta, \sin\theta)

Meaning

Coordinates of the point where the terminal side of angle θ\theta meets the unit circle.

Domain

Points on the unit circle x2+y2=1x^2+y^2=1.

y=tan⁡θy = \tan \theta

Clear evidence
Shown in the video
Evidence
  1. Formula
    Observation

    Top-left handwritten title reads y=tan⁡θy = \tan θ.

  2. Audio
    Observation

    The speaker refers to the shape of the graph of y is equal to tangent of theta.

Symbol

y=tan⁡θy = \tan \theta

Meaning

The plotted function whose value at angle θ is the tangent of θ.

Domain

θ is an angle in radians; y is the corresponding tangent value.

θ\theta

Clear evidence
Shown in the video
Evidence
  1. Formula
    Observation

    The table header uses θ.

  2. Audio
    Observation

    The speaker repeatedly says “if theta is...” while choosing example angles.

Symbol

θ\theta

Meaning

Input angle used to evaluate the tangent function and to draw a ray on the unit circle.

Domain

Angles shown in this clip include 0, π/4π/4, and -π/4 radians.

Knowledge points · 30

Goal: become familiar with the graph of y=tan⁡θy=\tan\theta

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says, "So what I hope to do in this video is get some familiarity with the graph of tangent of theta."

  2. Formula
    Observation

    The title y=tan⁡θy = \tan \theta is written at the upper left.

Definition
Explanation

This clip introduces the task of understanding the tangent graph by connecting it to the unit circle rather than by plotting points immediately. The visible target function is y=tan⁡θy=\tan\theta, and the large coordinate grid on the right is prepared for later graphing.

Formula
y=tan⁡θy = \tan \theta
Conditions
  1. The clip is introductory.

  2. No explicit domain restriction is stated in this segment.

Unit-circle setup for visualizing tangent values

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says he will set up a little unit circle so we can visualize what the tangent of various thetas are.

  2. Diagram
    Observation

    Teal axes and a circle centered at the origin are drawn on the left side.

Definition
Explanation

The instructor draws an auxiliary coordinate system and a circle centered at the origin to represent the unit circle. This construction is used as a geometric reference for interpreting tan⁡θ\tan\theta through coordinates and slope.

Formula
Conditions
  1. The circle is presented as a unit circle.

  2. The drawing is an auxiliary visualization beside the main graph grid.

Prerequisites
  1. Goal: become familiar with the graph of y=tan⁡θy=\tan\theta

Angle θ\theta formed from the positive xx-axis

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says, "if I have an angle, an angle theta, where one side is the positive x-axis".

  2. Diagram
    Observation

    A yellow ray is drawn from the origin into the first quadrant, forming an angle with the positive xx-axis.

Definition
Explanation

The angle θ\theta is represented in standard position: one side lies along the positive xx-axis and the other side is a ray from the origin. The clip uses this ray to connect an angle to a point on the unit circle.

Formula
Conditions
  1. One side of the angle is the positive xx-axis.

  2. The other side is a ray from the origin.

Prerequisites
  1. Unit-circle setup for visualizing tangent values

Point on the unit circle has coordinates (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta)

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says the coordinates where the ray intersects the unit circle are cosine theta comma sine theta, after correcting an initial slip.

  2. Formula
    Observation

    The point is labeled (cos⁡θ,sin⁡θ)(\cos\theta, \sin\theta).

Definition
Explanation

When the terminal side of θ\theta intersects the unit circle, the intersection point’s horizontal coordinate is cos⁡θ\cos\theta and its vertical coordinate is sin⁡θ\sin\theta. This is the bridge from angle measure to coordinate geometry used later for tangent.

Formula
(cos⁡θ, sin⁡θ)(\cos\theta,\ \sin\theta)
Conditions
  1. The point lies on the unit circle.

  2. The angle is measured from the positive xx-axis to the terminal ray.

Prerequisites
  1. Angle θ\theta formed from the positive xx-axis

Tangent identity tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says tangent of theta is the same thing as the sine of theta over the cosine of theta.

  2. Formula
    Observation

    The handwritten equation tan⁡θ=sin⁡θcos⁡θ\tan\theta = \frac{\sin\theta}{\cos\theta} is shown.

Formula
Explanation

The clip states the quotient identity for tangent. In the unit-circle picture, this means tangent is the ratio of the point’s yy-coordinate to its xx-coordinate.

Formula
tan⁡θ=sin⁡θcos⁡θ\tan\theta = \frac{\sin\theta}{\cos\theta}
Conditions
  1. The identity is used for the angle θ\theta shown on the unit circle.

  2. The clip does not explicitly mention the restriction cos⁡θ≠0\cos\theta\neq 0.

Prerequisites
  1. Point on the unit circle has coordinates (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta)

Tangent as the slope of the terminal ray

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says taking the y-coordinate over the x-coordinate is essentially the slope of this line, change in y over change in x.

  2. Formula
    Observation

    The handwritten slope expression ΔyΔx\frac{\Delta y}{\Delta x} is added beneath the tangent identity.

Method
Explanation

Because the ray starts at the origin and passes through (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta), the ratio sin⁡θcos⁡θ\frac{\sin\theta}{\cos\theta} is also the rise-over-run slope of that ray. This gives a geometric way to think about the size and sign of tan⁡θ\tan\theta.

Formula
tan⁡θ=ΔyΔx=sin⁡θcos⁡θ\tan\theta = \frac{\Delta y}{\Delta x} = \frac{\sin\theta}{\cos\theta}
Conditions
  1. The line/ray passes through the origin.

  2. The referenced point is the unit-circle intersection (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta).

  3. The clip does not explicitly discuss the undefined case when the run is zero.

Prerequisites
  1. Tangent identity tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}
  2. Point on the unit circle has coordinates (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta)

Transition from geometric explanation to tabulating values

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says, "So now let's make a table," and begins discussing various thetas and what tangent of theta would be.

  2. Diagram
    Observation

    The unit-circle annotations are cleaned up, and a new vertical yellow line is drawn at the far left as the start of a table.

Uncertainties
  1. The table headings and entries are not yet visible by the end of the clip.

Method
Explanation

After establishing that tangent can be read from the unit circle as a coordinate ratio or slope, the instructor clears space and begins a table. The intended next step is to list several angles θ\theta and determine the corresponding tan⁡θ\tan\theta values.

Formula
Conditions
  1. This is only the beginning of the table-making step within the clip.

  2. No completed table entries appear before 120 seconds.

Prerequisites
  1. Tangent as the slope of the terminal ray

Tangent interpreted as the slope of the terminal ray

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker explains tangent values by asking what the slope of the ray is.

  2. Diagram
    Observation

    Each chosen angle is represented by a ray from the origin of the unit circle.

Definition
Explanation

In this clip, the presenter treats tan⁡θ\tan \theta as the slope of the ray making angle θ\theta with the positive x-axis on the unit circle. The reasoning is visual: compare how much the ray rises vertically for a given horizontal run.

Formula
tan⁡θ=slope of the ray at angle θ\tan \theta = \text{slope of the ray at angle } \theta
Conditions
  1. θ is measured from the positive x-axis.

  2. The ray is drawn on the unit circle diagram.

Prerequisites
  1. Using a unit-circle ray to evaluate tangent

Using a unit-circle ray to evaluate tangent

Clear evidence
Shown in the video
Evidence
  1. Diagram
    Observation

    A cyan unit circle with x- and y-axes is shown, and yellow rays are drawn from the origin for selected angles.

  2. Audio
    Observation

    The speaker points to the ray while discussing its slope.

Method
Explanation

The method shown is to pick convenient angles, draw the corresponding terminal ray on the unit circle, and read off the tangent value from the ray’s slope or from the equality of coordinate changes.

Formula
Conditions
  1. A unit circle is available.

  2. Selected angles should have easily recognized coordinates or slopes.

Prerequisites
  1. Tangent interpreted as the slope of the terminal ray

Building a table of values before graphing

Clear evidence
Shown in the video
Evidence
  1. Formula
    Observation

    A two-column table labeled θ and tan θ is built on the left.

  2. Audio
    Observation

    The speaker says these values will help us think about the shape of the graph of y=tan⁡θy = \tan θ.

Method
Explanation

Before sketching the full graph, the video records sample input-output pairs in a table. This turns the geometric unit-circle information into numerical points that can later be transferred to the coordinate grid.

Formula
Conditions
  1. Useful when the goal is to infer the overall shape of a function graph from selected values.

Prerequisites
  1. Tangent interpreted as the slope of the terminal ray
  2. Using a unit-circle ray to evaluate tangent

Value of tangent at 0 radians

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says if theta is zero radians, the slope is zero because as x changes, y doesn't change at all.

  2. Formula
    Observation

    The first table row records θ=0θ = 0 and tan⁡θ=0\tan θ = 0.

Formula
Explanation

At θ=0\theta=0, the terminal ray lies along the positive x-axis, so there is no vertical change as the horizontal coordinate changes. Therefore the slope, and hence the tangent value, is 0.

Formula
tan⁡0=0\tan 0 = 0
Conditions
  1. θ=0θ = 0 radians.

Prerequisites
  1. Tangent interpreted as the slope of the terminal ray

Value of tangent at π/4π/4 radians

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says for pi over four radians, your x-coordinate and your y-coordinate is the same, so the slope of this ray is going to be equal to 1.

  2. Formula
    Observation

    The table records θ=π/4θ = π/4 and tan⁡θ=1\tan θ = 1.

Formula
Explanation

For θ=π4\theta=\frac{\pi}{4}, the unit-circle point has equal x- and y-coordinates, so moving horizontally and vertically by the same amount gives slope 1. The presenter also states that sin⁡θ\sin \theta and cos⁡θ\cos \theta are the same, so their ratio is 1.

Formula
tan⁡(π4)=1\tan\left(\frac{\pi}{4}\right)=1
Conditions
  1. θ=π/4θ = π/4 radians.

  2. Equivalently, the sine and cosine values are equal and nonzero.

Prerequisites
  1. Tangent interpreted as the slope of the terminal ray
  2. Tangent as sine divided by cosine
Claims and conditions · 16

Quotient identity for tangent

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker states that tangent of theta is the same thing as sine of theta over cosine of theta.

  2. Formula
    Observation

    The equation tan⁡θ=sin⁡θcos⁡θ\tan\theta = \frac{\sin\theta}{\cos\theta} is written on screen.

Uncertainties
  1. The video does not explicitly state the condition cos⁡θ≠0\cos\theta\neq 0 in this clip.

Proposition
Statement

For the angle θ\theta shown on the unit circle, tan⁡θ=sin⁡θcos⁡θ\tan\theta = \frac{\sin\theta}{\cos\theta}.

Hypotheses
  1. θ\theta is an angle in standard position on the unit circle.

  2. The point on the unit circle determined by θ\theta has coordinates (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta).

  3. The clip leaves unstated the usual requirement cos⁡θ≠0\cos\theta\neq 0 for the quotient to be defined.

Quantifiers

Stated for the angle θ\theta under discussion; no explicit universal quantifier is spoken in this clip.

Tangent equals the slope of the terminal ray

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says the y-coordinate over the x-coordinate is essentially the slope of this line, change in y over change in x.

  2. Formula
    Observation

    The slope expression ΔyΔx\frac{\Delta y}{\Delta x} is written alongside the tangent identity.

Uncertainties
  1. The spoken wording uses "this line" while the drawn object is a ray from the origin; the mathematical meaning is the slope of the terminal side.

Proposition
Statement

In the unit-circle setup, tan⁡θ\tan\theta is the slope of the ray from the origin through (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta), namely ΔyΔx\frac{\Delta y}{\Delta x}.

Hypotheses
  1. The ray begins at the origin.

  2. It intersects the unit circle at (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta).

  3. Slope is computed as change in yy divided by change in xx.

Quantifiers

Presented for the example angle θ\theta and the associated ray.

Horizontal ray has slope 0

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says if theta is zero radians, the slope is zero because as x changes, y doesn't change at all.

  2. Diagram
    Observation

    The ray for θ=0θ = 0 lies along the positive x-axis.

Proposition
Statement

If the terminal ray for θ lies along the positive x-axis, then its slope is 0, so tan⁡θ=0\tan \theta = 0.

Hypotheses
  1. θ=0θ = 0 radians.

  2. The ray is drawn from the origin along the positive x-direction.

Quantifiers

For the specific angle θ=0θ = 0 shown in the clip.

Equal sine and cosine imply tangent 1

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says your x-coordinate and your y-coordinate is the same ... so the slope of this ray ... is going to be equal to 1.

  2. Audio
    Observation

    He adds that sine of theta over cosine of theta are the same thing, so you get 1.

Proposition
Statement

When the x- and y-coordinates on the unit circle are equal and nonzero, the ray’s slope is 1, equivalently sin⁡θcos⁡θ=1\frac{\sin \theta}{\cos \theta}=1, so tan⁡θ=1\tan \theta=1.

Hypotheses
  1. The point lies on the unit circle.

  2. The x-coordinate equals the y-coordinate.

  3. The common cosine value is nonzero.

Quantifiers

Applied in the clip to θ=π/4θ = π/4.

Recorded tangent value for -π/4

Clear evidence
Shown in the video
Evidence
  1. Formula
    Observation

    The left table visibly contains the row θ=−π/4θ = -π/4, tan⁡θ=−1\tan θ = -1.

  2. Diagram
    Observation

    A fourth-quadrant ray is drawn for the negative angle.

Uncertainties
  1. The spoken justification is cut off before completion, but the written result is clear.

Proposition
Statement

The clip records tan⁡(−π4)=−1\tan\left(-\frac{\pi}{4}\right)=-1.

Hypotheses
  1. θ=−π/4θ = -π/4 radians.

Quantifiers

For the specific angle shown in the table.

Behavior of tan⁡θ\tan\theta as θ→π/2−\theta\to\pi/2^-

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 01:19.000 the speaker asks what happens as the angle gets closer and closer to π/2\pi/2.

  2. Audio
    Observation

    At 01:35.000 the speaker says the ray is getting closer and closer to approaching the vertical.

  3. Audio
    Observation

    At 01:40.000 the speaker says its slope is getting more and more and more positive.

  4. Audio
    Observation

    At 01:44.000 the speaker says at π/2\pi/2 the slope is undefined but is approaching infinity.

Proposition
Statement

As θ\theta approaches π/2\pi/2 from below, the tangent value grows without bound, so the graph has a vertical asymptote at θ=π/2\theta=\pi/2.

Hypotheses
  1. θ\theta is measured in radians.

  2. The approach is from values less than π/2\pi/2.

Quantifiers

For θ\theta tending to π/2\pi/2 from the left.

Vertical asymptote of the tangent graph at θ=π/2\theta=\pi/2

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 01:53.000 the speaker says, "So as you get closer and closer to pi over two ... I'm going to draw essentially a vertical asymptote right over here at pi over two".

  2. Diagram
    Observation

    A dashed vertical line is drawn at θ=π/2\theta=\pi/2 on the right-hand graph.

Proposition
Statement

The graph of y=tan⁡θy=\tan\theta has a vertical asymptote at θ=π/2\theta=\pi/2.

Hypotheses
  1. Graphing y=tan⁡θy=\tan\theta.

  2. Angles in radians.

Quantifiers

At the specific value θ=π/2\theta=\pi/2 shown in this clip.

Tangent is not defined at the marked asymptote location

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 00:00:38-00:00:42 the speaker says, “So once again, not quite defined right over there, we have a vertical asymptote.”

Uncertainties
  1. The clip states non-definition at the marked location but does not provide a formal algebraic proof in this excerpt.

Proposition
Statement

At the boundary angle being discussed, the tangent graph is not defined and the curve has a vertical asymptote there.

Hypotheses
  1. The angle is the boundary location shown on the graph near -π/2 or π/2π/2.

  2. The graph is being interpreted through the unit-circle slope picture used in the clip.

Quantifiers

Local statement about the specific boundary angle under discussion in the clip.

Approach to +∞\infty as θ→π/2θ \to π/2 from the left

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 00:00:13-00:00:18 the speaker says the slope gets closer and closer to π/2π/2 and is getting closer and closer to infinity.

  2. Diagram
    Observation

    The central red branch rises sharply toward the dashed line at θ=π/2θ = π/2.

Uncertainties
  1. The clip expresses the idea verbally and visually rather than writing a limit notation.

Proposition
Statement

As the angle approaches π/2π/2 from below, the slope of the corresponding ray, and hence the tangent value, grows without bound positively.

Hypotheses
  1. θ is approaching π/2π/2 from values less than π/2π/2.

  2. The tangent value is identified with the slope of the ray in the unit-circle picture.

Quantifiers

One-sided limiting behavior near π/2π/2.

Approach to -∞ as θ→−π/2θ \to -π/2 from the right

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 00:00:18-00:00:36 the speaker asks what happens as the angle gets closer and closer to negative π/2π/2 and answers that the slope is approaching negative infinity.

  2. Diagram
    Observation

    The central red branch descends sharply toward the dashed line at θ=−π/2θ = -π/2.

Uncertainties
  1. The clip expresses the idea verbally and visually rather than writing a limit notation.

Proposition
Statement

As the angle approaches -π/2 from above, the slope of the corresponding ray becomes more and more negative without bound.

Hypotheses
  1. θ is approaching -π/2 from values greater than -π/2.

  2. The tangent value is identified with the slope of the ray in the unit-circle picture.

Quantifiers

One-sided limiting behavior near -π/2.

Immediately after π/2π/2 the tangent graph restarts from very negative values

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 00:01:02-00:01:15 the speaker says that right after crossing π/2π/2 the slope is hugely negative.

  2. Audio
    Observation

    At 00:01:19-00:01:24 the speaker says the graph jumps back down here and is hugely negative again.

  3. Diagram
    Observation

    A new branch is started below the x-axis just to the right of the asymptote at π/2π/2.

Uncertainties
  1. The clip does not finish deriving the full next branch before ending.

Proposition
Statement

Just after the angle crosses π/2π/2, the corresponding slope is very large negative, so the graph of tangent drops to a new branch below the axis and then rises as θ increases.

Hypotheses
  1. θ is slightly greater than π/2π/2.

  2. The same unit-circle slope interpretation is being continued from the previous branch.

Quantifiers

Local statement about angles just to the right of π/2π/2.

Tangent value at 3π/43π/4

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says, “So at three pi over four, we have a slope of negative one.”

  2. Formula
    Observation

    The table already lists -π/4 with tan⁡θ=−1\tan θ = -1, and the speaker compares 3π/43π/4 to that slope.

Proposition
Statement

tan⁡(3π4)=−1\tan\left(\frac{3\pi}{4}\right)=-1.

Hypotheses
  1. θ is measured in radians.

  2. The angle 3π/43π/4 is on the unit circle.

  3. Tangent is interpreted as the slope of the terminal ray.

Quantifiers

For the specific angle θ=3π/4θ = 3π/4.

Derivations and proofs · 10

Deriving the slope interpretation of tangent from the unit circle

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker moves from the point (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta) to tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta} and then to slope ΔyΔx\frac{\Delta y}{\Delta x}.

  2. Formula
    Observation

    The screen shows (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta), then tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}, then ΔyΔx\frac{\Delta y}{\Delta x}.

Intuitive argument
Steps
  1. Expression
    (cos⁡θ, sin⁡θ)(\cos\theta,\ \sin\theta)
    Explanation

    The terminal ray of angle θ\theta meets the unit circle at a point whose coordinates are cosine theta and sine theta.

    Justification

    Unit-circle definition of sine and cosine, stated by the speaker.

    Shown in the video
  2. Expression
    tan⁡θ=sin⁡θcos⁡θ\tan\theta = \frac{\sin\theta}{\cos\theta}
    Explanation

    Tangent is rewritten as the ratio of the point’s yy-coordinate to its xx-coordinate.

    Justification

    Quotient identity for tangent, written and spoken in the clip.

    Shown in the video
  3. Expression
    ΔyΔx\frac{\Delta y}{\Delta x}
    Explanation

    Because the ray starts at the origin, that same coordinate ratio is the rise over run of the ray.

    Justification

    Definition of slope as change in yy divided by change in xx, explained verbally and written on screen.

    Shown in the video
Conclusion

The clip connects three equivalent viewpoints: the unit-circle coordinates, the quotient identity for tangent, and the slope of the terminal ray.

Deriving sample tangent values from unit-circle slopes

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker repeatedly computes tangent by asking what the slope of the ray is.

  2. Diagram
    Observation

    Rays and small right triangles are drawn on the unit circle for selected angles.

Visual argument
Steps
  1. Expression
    Explanation

    Choose an angle θ and draw its terminal ray from the origin of the unit circle.

    Justification

    This is the setup shown on the left diagram.

    Shown in the video
  2. Expression
    Explanation

    Read the ray’s vertical change relative to its horizontal change, i.e. its slope.

    Justification

    The speaker explicitly interprets tangent as the slope of the ray.

    Shown in the video
  3. Expression
    tan⁡0=0\tan 0 = 0
    Explanation

    For θ=0θ = 0, the ray is horizontal, so y does not change as x changes.

    Justification

    Stated directly in the audio and matched by the drawn ray.

    Shown in the video
  4. Expression
    tan⁡(π4)=1\tan\left(\frac{\pi}{4}\right)=1
    Explanation

    For θ=π/4θ = π/4, the x- and y-coordinates are the same, so the rise equals the run and the slope is 1.

    Justification

    Explained verbally using equal coordinates and the identity sin⁡θ/cos⁡θ\sin θ / \cos θ.

    Shown in the video
  5. Expression
    tan⁡(−π4)=−1\tan\left(-\frac{\pi}{4}\right)=-1
    Explanation

    For θ=−π/4θ = -π/4, the ray goes downward while moving right, giving a negative slope of magnitude 1.

    Justification

    The table entry is written explicitly; the verbal explanation begins but the clip ends before it is fully completed.

    Shown in the video
Conclusion

The sample values tabulated in the clip are tan⁡0=0\tan 0 = 0, tan⁡(π/4)=1\tan(\pi/4)=1, and tan⁡(−π/4)=−1\tan(-\pi/4)=-1.

Using sin⁡/cos⁡\sin /\cos to confirm tangent at π/4π/4

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says tangent of theta is going to be equal to 1, or sine of theta over cosine of theta, they're the same thing, so you're going to get 1.

Intuitive argument
Steps
  1. Expression
    tan⁡θ=sin⁡θcos⁡θ\tan \theta = \frac{\sin \theta}{\cos \theta}
    Explanation

    Rewrite tangent as the quotient of sine and cosine.

    Justification

    This identity is stated aloud by the presenter.

    Shown in the video
  2. Expression
    Explanation

    At θ=π/4θ = π/4, the sine and cosine values are the same.

    Justification

    The speaker says the x-coordinate and y-coordinate are the same and mentions √2/22/2 for both.

    Shown in the video
  3. Expression
    sin⁡(π/4)cos⁡(π/4)=1\frac{\sin(\pi/4)}{\cos(\pi/4)} = 1
    Explanation

    Dividing equal nonzero quantities gives 1.

    Justification

    Direct arithmetic consequence of equality of numerator and denominator.

    Derived from the video
Conclusion

This confirms tan⁡(π/4)=1\tan(\pi/4)=1 without relying only on the visual slope argument.

Deriving tan⁡(−π/4)=−1\tan(-\pi/4)=-1 from unit-circle coordinates

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 00:00.000 the speaker says sine and cosine of the angle are opposites.

  2. Audio
    Observation

    At 00:04.000 the speaker gives cosine as 2/2\sqrt{2}/2 and at 00:10.000 gives the yy-coordinate as −2/2-\sqrt{2}/2.

  3. Audio
    Observation

    At 00:18.000 the speaker computes tangent as sine over cosine and obtains −1-1.

Intuitive argument
Steps
  1. Expression
    cos⁡θ=22,sin⁡θ=−22\cos\theta=\frac{\sqrt{2}}{2},\quad \sin\theta=-\frac{\sqrt{2}}{2}
    Explanation

    From the unit-circle point for the angle, the xx-coordinate is positive 2/2\sqrt{2}/2 and the yy-coordinate is negative 2/2\sqrt{2}/2.

    Justification

    Directly stated in the audio at 00:04.000-00:17.000.

    Shown in the video
  2. Expression
    tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}
    Explanation

    The tangent is formed as the ratio of sine to cosine.

    Justification

    Stated in the audio at 00:18.000-00:23.000.

    Shown in the video
  3. Expression
    tan⁡(−π4)=−2222=−1\tan\left(-\frac{\pi}{4}\right)=\frac{-\frac{\sqrt{2}}{2}}{\frac{\sqrt{2}}{2}}=-1
    Explanation

    Substituting the two coordinates gives a quotient of −1-1.

    Justification

    Algebraic simplification of the displayed ratio; the final value is also written into the table by 00:45.000.

    Derived from the video
Conclusion

The tangent value for the angle −π/4-\pi/4 is −1-1.

Explaining the vertical asymptote at θ=π/2\theta=\pi/2

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 01:19.000 the speaker asks what happens as the angle gets closer to π/2\pi/2.

  2. Audio
    Observation

    At 01:35.000 the speaker says the ray approaches vertical.

  3. Audio
    Observation

    At 01:40.000 the speaker says the slope becomes more and more positive.

  4. Audio
    Observation

    At 01:44.000 the speaker says the slope at π/2\pi/2 is undefined but approaching infinity.

  5. Diagram
    Observation

    At 01:53.000-02:00.000 a dashed vertical asymptote is drawn at θ=π/2\theta=\pi/2.

Visual argument
Steps
  1. Expression
    θ→π2−\theta\to\frac{\pi}{2}^{-}
    Explanation

    The angle is increased toward π/2\pi/2 from smaller values.

    Justification

    Stated in the audio beginning at 01:19.000.

    Shown in the video
  2. Expression
    ray becomes more nearly vertical\text{ray becomes more nearly vertical}
    Explanation

    On the unit circle, the terminal ray approaches the vertical direction.

    Justification

    Stated in the audio at 01:35.000-01:40.000.

    Shown in the video
  3. Expression
    tan⁡θ=slope of the ray→+∞\tan\theta=\text{slope of the ray}\to +\infty
    Explanation

    Because tangent is interpreted as the slope of the terminal ray, the slope grows without bound as the ray nears vertical.

    Justification

    Stated in the audio at 01:40.000-01:52.000.

    Shown in the video
  4. Expression
    θ=π2 is a vertical asymptote\theta=\frac{\pi}{2}\ \text{is a vertical asymptote}
    Explanation

    The unbounded growth is represented on the graph by a dashed vertical line at π/2\pi/2.

    Justification

    Drawn and described in the audio at 01:53.000-02:00.000.

    Shown in the video
Conclusion

The tangent graph develops a vertical asymptote at θ=π/2\theta=\pi/2 because the corresponding ray becomes vertical and its slope tends to infinity.

Deriving the shape of the central tangent branch from ray-slope behavior

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 00:00:02-00:00:18 the speaker explains approach to infinity near π/2π/2.

  2. Audio
    Observation

    At 00:00:18-00:00:36 the speaker explains approach to negative infinity near -π/2.

  3. Diagram
    Observation

    The red curve is drawn between the two dashed asymptotes and through the origin.

Intuitive argument
Steps
  1. Expression
    Explanation

    Start from the unit-circle picture: a ray from the origin represents the angle θ, and the lesson treats tan θ as the slope of that ray.

    Justification

    Explicitly stated in the audio at 00:00:13-00:00:18 and supported by the left-hand diagram.

    Shown in the video
  2. Expression
    Explanation

    As θ moves closer to π/2π/2, the ray becomes steeper and steeper in the positive direction, so the slope tends to +∞\infty .

    Justification

    Directly stated by the speaker at 00:00:13-00:00:18 and shown by the rising right end of the red branch.

    Shown in the video
  3. Expression
    Explanation

    As θ moves closer to -π/2, the ray becomes steeper and steeper in the negative direction, so the slope tends to -∞.

    Justification

    Directly stated by the speaker at 00:00:18-00:00:36 and shown by the falling left end of the red branch.

    Shown in the video
  4. Expression
    Explanation

    Therefore the graph on the interval between -π/2 and π/2π/2 is a single increasing branch passing through the origin and bounded by vertical asymptotes at both ends.

    Justification

    This is the visual conclusion assembled from the preceding slope descriptions and the drawn curve.

    Derived from the video
Conclusion

The central branch of y=tan⁡θy = \tan θ is obtained by translating the unbounded positive and negative slope behavior near ±π/2π/2 into a graph with vertical asymptotes at those angles.

Why the graph restarts below the axis just after π/2π/2

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 00:00:51-00:01:01 the speaker says the graph can keep going beyond the displayed section.

  2. Audio
    Observation

    At 00:01:02-00:01:15 the speaker analyzes the angle just after crossing π/2π/2 and calls the slope hugely negative.

  3. Audio
    Observation

    At 00:01:19-00:01:24 the speaker says the graph jumps back down and is hugely negative again.

  4. Diagram
    Observation

    A new red branch begins below the axis to the right of the asymptote at π/2π/2.

Uncertainties
  1. The derivation is only partially completed before the clip ends.

Intuitive argument
Steps
  1. Expression
    Explanation

    Consider an angle just larger than π/2π/2 on the unit circle.

    Justification

    Explicitly introduced by the speaker at 00:01:02-00:01:09.

    Shown in the video
  2. Expression
    Explanation

    The corresponding ray now points into the second quadrant, where its slope is negative and very large in magnitude.

    Justification

    Stated by the speaker at 00:01:10-00:01:18 as “hugely negative.”

    Shown in the video
  3. Expression
    Explanation

    Thus the tangent graph does not continue upward through the asymptote; instead it reappears on a new branch far below the x-axis.

    Justification

    Stated by the speaker at 00:01:19-00:01:24 and shown by the newly drawn lower branch.

    Shown in the video
  4. Expression
    Explanation

    As θ continues to increase past π/2π/2, the slope becomes less negative, so the new branch rises.

    Justification

    Stated by the speaker at 00:01:24-00:01:33.

    Shown in the video
Conclusion

Immediately after π/2π/2, the tangent graph jumps to a new branch starting from very negative values and then increases as the angle grows.

Deriving tan⁡(3π/4)\tan (3π/4) from unit-circle geometry

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker derives 3π/43π/4 from π/2π/2 plus π/4π/4 and then explains the quadrant signs.

  2. Diagram
    Observation

    The unit circle shows a second-quadrant ray and the handwritten label 3π/43π/4.

Intuitive argument
Steps
  1. Expression
    2π4+π4=3π4\frac{2\pi}{4}+\frac{\pi}{4}=\frac{3\pi}{4}
    Explanation

    The speaker rewrites π/2π/2 as 2π/42π/4 and adds another π/4π/4 to identify the angle 3π/43π/4.

    Justification

    Arithmetic on radian measures.

    Shown in the video
  2. Expression
    45∘-45∘-90∘ triangle45^\circ\text{-}45^\circ\text{-}90^\circ\text{ triangle}
    Explanation

    He notes that this angle forms another 45-45-90 triangle, so the horizontal and vertical distances have the same magnitude.

    Justification

    Special right-triangle geometry on the unit circle.

    Shown in the video
  3. Expression
    x<0, y>0x<0,\ y>0
    Explanation

    Because the terminal ray lies in the second quadrant, the x-distance is negative and the y-distance is positive.

    Justification

    Quadrant sign convention on the coordinate plane.

    Shown in the video
  4. Expression
    tan⁡(3π4)=−1\tan\left(\frac{3\pi}{4}\right)=-1
    Explanation

    Equal magnitudes with opposite signs give a ratio of -1, matching the slope previously seen at -π/4.

    Justification

    Tangent is treated as slope, or rise over run, on the terminal ray.

    Shown in the video
Conclusion

The video concludes that the tangent value at 3π/43π/4 is -1.

Extending the tangent graph from 3π/43π/4 through π to the next special angle

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker moves from 3π/43π/4 to π and then by another π/4π/4, stating the slope returns to 0 and then to positive 1.

  2. Diagram
    Observation

    Plotted points appear at θ=πθ = π, y=0y = 0 and near θ=5π/4θ = 5π/4, y=1y = 1.

Uncertainties
  1. The exact symbolic label 5π/45π/4 is not separately written in the visible frames, though the spoken increment and plotted point support it.

Visual argument
Steps
  1. Expression
    θ=3π4, tan⁡θ=−1\theta=\frac{3\pi}{4},\ \tan\theta=-1
    Explanation

    Starting from the just-derived point, the graph has a negative unit slope value.

    Justification

    Previous derivation in the clip.

    Shown in the video
  2. Expression
    θ=π, tan⁡θ=0\theta=\pi,\ \tan\theta=0
    Explanation

    As the angle increases to π, the terminal ray lies horizontally and the slope returns to zero.

    Justification

    Geometric position of the terminal ray on the unit circle.

    Shown in the video
  3. Expression
    θ=π+π4=5π4, tan⁡θ=1\theta=\pi+\frac{\pi}{4}=\frac{5\pi}{4},\ \tan\theta=1
    Explanation

    Increasing by another π/4π/4 puts the ray in the third quadrant, where both coordinate changes have the same sign, restoring a positive unit slope.

    Justification

    Symmetry of the unit circle and the slope interpretation of tangent.

    Derived from the video
Conclusion

The plotted tangent values progress from -1 at 3π/43π/4 to 0 at π and then to 1 at 5π/45π/4.

From unbounded growth to periodic repetition and asymptotes

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says the slope approaches positive infinity near 3π/23π/2, then says the pattern continues every pi radians and draws asymptotes.

  2. Diagram
    Observation

    A steep branch rises toward a dashed vertical line at 3π/23π/2, and similar branches are drawn in other π-length intervals.

Visual argument
Steps
  1. Expression
    θ→3π2−⇒tan⁡θ→+∞\theta\to\frac{3\pi}{2}^- \Rightarrow \tan\theta\to+\infty
    Explanation

    Near 3π/23π/2, a small movement in x corresponds to a very large movement upward in y, so the tangent value grows without bound.

    Justification

    Spoken description of steepening slope and visible curve behavior.

    Shown in the video
  2. Expression
    θ=3π2 is drawn as a dashed vertical asymptote\theta=\frac{3\pi}{2}\text{ is drawn as a dashed vertical asymptote}
    Explanation

    The graph is separated at that angle by a dashed vertical line.

    Justification

    Visual construction in the clip.

    Shown in the video
  3. Expression
    repeat every π radians\text{repeat every }\pi\text{ radians}
    Explanation

    The same branch shape is then reproduced in adjacent intervals of length π.

    Justification

    Explicit spoken periodicity claim plus repeated drawing.

    Shown in the video
Conclusion

The clip uses unbounded behavior near 3π/23π/2 to justify drawing vertical asymptotes and repeating the tangent graph every π radians.

Worked examples · 4

Example: choosing easy angles to sketch y=tan⁡θy = \tan θ

Clear evidence
Shown in the video
Evidence
  1. Formula
    Observation

    The left table accumulates rows (0,0), (π/4π/4,1), and (-π/4,-1).

  2. Audio
    Observation

    The speaker says he is picking values that are very easy for us to think about and that will help form the shape of the graph.

Uncertainties
  1. The final verbal explanation for the -π/4 case is incomplete because the clip ends mid-sentence.

Problem

Select convenient angles, determine their tangent values from the unit circle, and record them in a table to prepare for graphing y=tan⁡θy = \tan θ.

Given
  1. A unit circle diagram is available.

  2. The target function is y=tan⁡θy = \tan θ.

  3. Chosen angles are 0, π/4π/4, and -π/4.

Goal

Compute and tabulate corresponding tangent values.

Steps
  1. Expression
    θ=0⇒tan⁡θ=0\theta = 0 \Rightarrow \tan \theta = 0
    Explanation

    The ray at 0 radians is horizontal, so its slope is 0.

    Justification

    Stated directly in the audio and written in the table.

    Shown in the video
  2. Expression
    θ=π4⇒tan⁡θ=1\theta = \frac{\pi}{4} \Rightarrow \tan \theta = 1
    Explanation

    At π/4π/4 the coordinates are equal, so rise equals run and the slope is 1.

    Justification

    Explained using both the unit-circle picture and sin⁡θ/cos⁡θ\sin θ / \cos θ.

    Shown in the video
  3. Expression
    θ=−π4⇒tan⁡θ=−1\theta = -\frac{\pi}{4} \Rightarrow \tan \theta = -1
    Explanation

    At -π/4 the ray points into the fourth quadrant, giving a negative slope of magnitude 1.

    Justification

    The result is written in the table; the spoken justification begins but is cut off.

    Shown in the video
Answer

The table contains (0,0)(0,0), (π4,1)(\frac{\pi}{4},1), and (−π4,−1)(-\frac{\pi}{4},-1).

Verification

Each entry matches the drawn ray direction on the unit circle and the slope-based interpretation used throughout the clip.

Plotting initial tangent values from the table

Clear evidence
Shown in the video
Evidence
  1. Formula
    Observation

    By 00:45.000 the table contains −π/4↦−1-\pi/4\mapsto -1, 0↦00\mapsto 0, and π/4↦1\pi/4\mapsto 1.

  2. Audio
    Observation

    At 00:46.000 the speaker says, "let's just start plotting a few of these points".

  3. Diagram
    Observation

    Between 00:58.000 and 01:11.000 the three corresponding points are plotted on the right-hand graph.

Problem

Use the known tangent values in the table to begin graphing y=tan⁡θy=\tan\theta.

Given
  1. tan⁡(−π/4)=−1\tan(-\pi/4)=-1

  2. tan⁡(0)=0\tan(0)=0

  3. tan⁡(π/4)=1\tan(\pi/4)=1

  4. Horizontal axis is θ\theta and vertical axis is yy.

Goal

Place the first points of the tangent graph on the coordinate grid.

Steps
  1. Expression
    (−π4,−1)(-\frac{\pi}{4},-1)
    Explanation

    Plot the point corresponding to tangent of negative π/4\pi/4.

    Justification

    Given by the table and stated in the audio at 01:07.000.

    Shown in the video
  2. Expression
    (0,0)(0,0)
    Explanation

    Plot the origin point corresponding to tangent of zero.

    Justification

    Given by the table and stated in the audio at 00:58.000.

    Shown in the video
  3. Expression
    (π4,1)(\frac{\pi}{4},1)
    Explanation

    Plot the point corresponding to tangent of π/4\pi/4.

    Justification

    Given by the table and stated in the audio at 01:03.000.

    Shown in the video
Answer

The graph starts with the three points (−π/4,−1)(-\pi/4,-1), (0,0)(0,0), and (π/4,1)(\pi/4,1).

Verification

These points match the completed table entries visible by 00:45.000 and the plotted marks visible by 01:11.000.

Introducing 3π/43π/4 as the next example angle

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 00:01:33-00:01:52 the speaker introduces an angle and says, “Let’s say that this angle right over here is 3π/43π/4.”

  2. Audio
    Observation

    At 00:01:53-00:01:59 the speaker begins explaining why 3π/43π/4 was chosen: “because that is π/2π/2 plus π/4π/4.”

  3. Formula
    Observation

    Handwritten 3π/43π/4 appears below the table near the end of the clip.

Uncertainties
  1. The example is only begun; no final tangent value or completed graph point for 3π/43π/4 is shown within this clip.

Problem

Choose a sample angle just beyond π/2π/2 to continue explaining the next branch of the tangent graph.

Given
  1. The current discussion is on angles just after crossing π/2π/2.

  2. The speaker selects the angle 3π/43π/4.

Goal

Use 3π/43π/4 to illustrate how the tangent graph behaves in the next interval after the asymptote.

Steps
  1. Expression
    Explanation

    The speaker first notes that the graph can keep going beyond the central section.

    Justification

    Audio at 00:00:51-00:01:01.

    Shown in the video
  2. Expression
    Explanation

    He then considers an angle just after crossing π/2π/2 and observes that its slope is hugely negative.

    Justification

    Audio at 00:01:02-00:01:18.

    Shown in the video
  3. Expression
    Explanation

    To make the next example concrete, he names the angle 3π/43π/4.

    Justification

    Audio at 00:01:47-00:01:52 and handwritten 3π/43π/4 near the end.

    Shown in the video
  4. Expression
    3π4=π2+π4\frac{3\pi}{4}=\frac{\pi}{2}+\frac{\pi}{4}
    Explanation

    He begins to justify the choice by rewriting 3π/43π/4 as π/2π/2 plus π/4π/4.

    Justification

    Audio at 00:01:53-00:01:59.

    Shown in the video
Answer

The clip identifies 3π/43π/4 as the next example angle and starts explaining it as π/2+π/4π/2 + π/4, but the worked consequence is not completed within the provided duration.

Verification

No completed numerical check or final plotted value for 3π/43π/4 is visible in this excerpt.

Plotting tangent values from 3π/43π/4 to the next special angle

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker names the angles 3π/43π/4, π, and the next π/4π/4 increment and states their slopes.

  2. Diagram
    Observation

    Red points are added on the right graph at (3π/43π/4,-1), (π,0), and approximately (5π/45π/4,1).

Uncertainties
  1. The third plotted angle is visually consistent with 5π/45π/4, but the exact label is not separately written on screen.

Problem

Use the unit-circle slope idea to place several points of y=tan⁡θy = \tan θ on the graph beyond π/2π/2.

Given
  1. The table already contains (-π/4,-1), (0,0), and (π/4π/4,1).

  2. The speaker identifies 3π/43π/4 by adding π/4π/4 to π/2π/2.

  3. Tangent is interpreted as slope of the terminal ray.

Goal

Determine and plot the tangent values at 3π/43π/4, π, and the next π/4π/4 increment.

Steps
  1. Expression
    tan⁡(3π4)=−1\tan\left(\frac{3\pi}{4}\right)=-1
    Explanation

    The second-quadrant 45-45-90 setup gives equal magnitudes with x negative and y positive, so the slope is -1.

    Justification

    Unit-circle geometry and quadrant signs.

    Shown in the video
  2. Expression
    (3π4,−1)(\frac{3\pi}{4},-1)
    Explanation

    This ordered pair is plotted on the θ-y graph.

    Justification

    Direct translation from angle and tangent value to graph coordinates.

    Shown in the video
  3. Expression
    tan⁡(π)=0\tan(\pi)=0
    Explanation

    At π the terminal ray is horizontal, so the slope returns to zero.

    Justification

    Geometric position on the unit circle.

    Shown in the video
  4. Expression
    (π,0)(\pi,0)
    Explanation

    The point at θ=πθ = π is plotted on the horizontal axis.

    Justification

    Graphing the computed tangent value.

    Shown in the video
  5. Expression
    tan⁡(5π4)=1\tan\left(\frac{5\pi}{4}\right)=1
    Explanation

    After increasing by another π/4π/4, the slope is positive one again.

    Justification

    Spoken continuation of the unit-circle pattern and visible plotted point.

    Derived from the video
Answer

The example produces the plotted points (3π/43π/4,-1), (π,0), and approximately (5π/45π/4,1).

Verification

The plotted red points match the spoken slope values and align with the grid labels on the θ-axis and y-axis.

Visual events · 21

Prepared graphing environment for tangent

Clear evidence
Shown in the video
Evidence
  1. Diagram
    Observation

    A large white coordinate grid occupies the right half of the screen, with x-axis labels from −2π-2\pi to 2π2\pi in multiples of π/4\pi/4 and y-axis labels from −4-4 to 44.

  2. Formula
    Observation

    The handwritten title y=tan⁡θy=\tan\theta appears at the upper left.

Objects
  1. Large Cartesian grid on the right

  2. Axis tick labels in radians

  3. Handwritten function title y=tan⁡θy=\tan\theta

Changes
  1. The title is written at the upper left.

  2. The right-side grid remains empty of a plotted curve during this clip.

Invariants
  1. The right grid stays fixed as the eventual graphing area.

  2. No tangent curve is drawn yet.

Interpretation

The visual layout separates the conceptual workspace on the left from the future graphing area on the right, signaling that the lesson will build understanding before plotting.

Auxiliary unit circle is drawn

Clear evidence
Shown in the video
Evidence
  1. Diagram
    Observation

    Teal axes are drawn on the left, followed by a circle centered at their intersection.

  2. Audio
    Observation

    The speaker says he is setting up a little unit circle to visualize tangent values.

Objects
  1. Teal vertical axis

  2. Teal horizontal axis

  3. Circle centered at the origin

Changes
  1. Axes are added on the left side.

  2. A circle is drawn around the origin.

Invariants
  1. The main right-hand grid is unchanged.

  2. The circle is presented as a unit circle.

Interpretation

The new left-side diagram serves as a geometric model for converting an angle into coordinates and then into a tangent value.

Standard-position angle θ\theta is illustrated

Clear evidence
Shown in the video
Evidence
  1. Diagram
    Observation

    A yellow ray is drawn from the origin into the first quadrant, and the angle between the positive xx-axis and the ray is marked θ\theta.

  2. Audio
    Observation

    The speaker describes an angle theta where one side is the positive x-axis.

Objects
  1. Positive xx-axis

  2. Yellow terminal ray

  3. Angle mark θ\theta

Changes
  1. A ray is added from the origin.

  2. The angle label θ\theta appears between the axes and the ray.

Invariants
  1. The circle remains centered at the origin.

  2. The initial side stays on the positive xx-axis.

Interpretation

The picture instantiates the abstract angle as a concrete ray, preparing to locate its intersection with the unit circle.

Coordinate point and slope triangle are annotated

Clear evidence
Shown in the video
Evidence
  1. Formula
    Observation

    The intersection point is labeled (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta).

  2. Diagram
    Observation

    Dashed guide lines form a right triangle from the origin to the point, and ΔyΔx\frac{\Delta y}{\Delta x} is written.

Objects
  1. Point (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta) on the circle

  2. Dashed horizontal and vertical guide segments

  3. Right triangle with legs along the axes directions

  4. Written ratios sin⁡θcos⁡θ\frac{\sin\theta}{\cos\theta} and ΔyΔx\frac{\Delta y}{\Delta x}

Changes
  1. The intersection point receives coordinate labels.

  2. Dashed segments create a right triangle.

  3. Slope notation is added beneath the tangent identity.

Invariants
  1. The point remains on the unit circle.

  2. The ray still starts at the origin.

Interpretation

The visual triangle makes the algebraic identities geometric: the vertical leg represents sin⁡θ\sin\theta or Δy\Delta y, the horizontal leg represents cos⁡θ\cos\theta or Δx\Delta x, and their ratio is the slope, hence tan⁡θ\tan\theta.

Shift from diagram to value table

Clear evidence
Shown in the video
Evidence
  1. Diagram
    Observation

    The detailed annotations around the unit circle are erased, leaving a simpler circle-and-ray sketch.

  2. Diagram
    Observation

    A new vertical yellow line is drawn at the far left as the beginning of a table.

  3. Audio
    Observation

    The speaker says, "So now let's make a table."

Uncertainties
  1. The table contents are not yet written by the end of the clip.

Objects
  1. Simplified unit-circle sketch

  2. New vertical yellow line at far left

Changes
  1. Extra labels and dashed guides are removed.

  2. A fresh column-like line is drawn to begin a table.

Invariants
  1. The unit circle remains as the conceptual reference.

  2. The right-hand graph grid is still unused.

Interpretation

The instructor transitions from explaining why tangent has a geometric meaning to organizing specific angle-value pairs for graphing.

Overall whiteboard layout for constructing the tangent graph

Clear evidence
Shown in the video
Evidence
  1. Diagram
    Observation

    The screen is split into three regions: a left handwritten table, a middle unit circle, and a right blank coordinate grid.

  2. Formula
    Observation

    The left table headers are θ and tan θ.

Objects
  1. Left two-column table labeled θ and tan θ

  2. Middle unit circle with x- and y-axes

  3. Right Cartesian grid with x-axis marked from -2π to 2π and y-axis from -4 to 4

  4. Title y=tan⁡θy = \tan θ

Changes
  1. The table is filled row by row as angles are discussed.

  2. Yellow rays are added to the unit circle for each chosen angle.

Invariants
  1. The unit circle remains centered at the origin.

  2. The right graph stays blank throughout this clip.

Interpretation

The visual organization separates numerical recording, geometric reasoning, and eventual graph plotting.

Ray for θ=0θ = 0

Clear evidence
Shown in the video
Evidence
  1. Diagram
    Observation

    A yellow ray lies along the positive x-axis of the unit circle.

  2. Formula
    Observation

    The first table row records 0 under θ and 0 under tan θ.

Objects
  1. Positive x-axis ray

  2. Table row (0,0)

Changes
  1. The first input-output pair is entered into the table.

Invariants
  1. The ray coincides with the horizontal axis.

Interpretation

This visually demonstrates zero vertical change, hence slope 0 and tan⁡0=0\tan 0 = 0.

Ray for θ=π/4θ = π/4

Clear evidence
Shown in the video
Evidence
  1. Diagram
    Observation

    A yellow ray is drawn into the first quadrant at 45 degrees, and a small right triangle is sketched near it.

  2. Formula
    Observation

    The table later records π/4π/4 under θ and 1 under tan θ.

Uncertainties
  1. The exact handwritten angle label on the circle is less clear than the spoken value and the table entry.

Objects
  1. First-quadrant ray

  2. Small right triangle indicating equal horizontal and vertical legs

  3. Table row (π/4π/4,1)

Changes
  1. A new ray is added above the x-axis.

  2. The corresponding tangent value 1 is written in the table.

Invariants
  1. The ray starts at the origin and meets the unit circle in the first quadrant.

Interpretation

Equal leg lengths show slope 1, matching tan⁡(π/4)=1\tan (π/4)=1.

Ray for θ=−π/4θ = -π/4

Clear evidence
Shown in the video
Evidence
  1. Diagram
    Observation

    A yellow ray is drawn into the fourth quadrant below the positive x-axis.

  2. Formula
    Observation

    The table records -π/4 under θ and -1 under tan θ.

Uncertainties
  1. The spoken explanation of why the value is negative is incomplete because the clip ends mid-sentence.

Objects
  1. Fourth-quadrant ray

  2. Table row (-π/4,-1)

Changes
  1. A downward-sloping ray is added.

  2. The tangent value -1 is entered in the table.

Invariants
  1. The ray still originates at the center of the unit circle.

Interpretation

The downward direction relative to rightward motion indicates a negative slope, consistent with tan⁡(−π/4)=−1\tan (-π/4)=-1.

Erasing auxiliary unit-circle marks

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 00:31.000 the speaker says, "let me clean this up a little bit because I want to keep reusing my unit circle".

  2. Animation
    Observation

    The extra construction marks around the unit circle are erased, leaving a cleaner circle and axes.

Objects
  1. Unit circle

  2. Terminal ray for −π/4-\pi/4

  3. Coordinate axes

Changes
  1. Temporary construction marks are removed.

  2. The unit circle is preserved for reuse.

Invariants
  1. The underlying angle value and tangent result remain unchanged.

Interpretation

This visual cleanup separates the computation stage from the upcoming graphing stage.

Plotting the first three tangent points

Clear evidence
Shown in the video
Evidence
  1. Diagram
    Observation

    Three points appear on the right-hand grid at θ=0\theta=0, θ=π/4\theta=\pi/4, and θ=−π/4\theta=-\pi/4 with y=0,1,−1y=0,1,-1 respectively.

  2. Audio
    Observation

    The speaker names each value as it is plotted between 00:58.000 and 01:11.000.

Objects
  1. Right-hand coordinate grid

  2. Point (0,0)(0,0)

  3. Point (π/4,1)(\pi/4,1)

  4. Point (−π/4,−1)(-\pi/4,-1)

Changes
  1. Points are added one by one onto the graph.

  2. The horizontal axis is identified as θ\theta and the vertical axis as yy.

Invariants
  1. The scale markings in multiples of π/4\pi/4 remain fixed.

Interpretation

The graph is initialized using exact values already computed from the unit circle.

Drawing the asymptote at θ=π/2\theta=\pi/2

Clear evidence
Shown in the video
Evidence
  1. Diagram
    Observation

    A dashed vertical line is drawn at θ=π/2\theta=\pi/2 on the right-hand graph.

  2. Audio
    Observation

    At 01:53.000 the speaker says he is drawing "essentially a vertical asymptote right over here at pi over two".

Objects
  1. Dashed vertical line

  2. Graph grid

  3. Label π/2\pi/2 on horizontal axis

Changes
  1. A new vertical guide appears at θ=π/2\theta=\pi/2.

  2. The graphing discussion shifts from discrete points to limiting behavior.

Invariants
  1. Previously plotted points remain in place.

Interpretation

The dashed line visually encodes that tan⁡θ\tan\theta becomes unbounded as θ\theta approaches π/2\pi/2.

Misconceptions · 9

Do not swap the unit-circle coordinates

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker initially says the coordinates are the sine of theta, then immediately corrects himself: "Sorry, the x coordinate is the cosine of theta."

Misconception

One may mistakenly think the xx-coordinate of the unit-circle point is sin⁡θ\sin\theta.

Clarification

The clip explicitly corrects this: the xx-coordinate is cos⁡θ\cos\theta and the yy-coordinate is sin⁡θ\sin\theta, so the point is (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta).

Tangent is not only an abstract fraction

Clear evidence
Derived from the video
Evidence
  1. Audio
    Observation

    The speaker emphasizes that taking y over x is essentially the slope of the line.

  2. Formula
    Observation

    ΔyΔx\frac{\Delta y}{\Delta x} is written next to tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}.

Misconception

Students may treat tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta} purely as an algebraic formula and miss its geometric meaning.

Clarification

In this unit-circle setup, the same ratio is the slope of the terminal ray, which helps visualize how tangent changes with angle. This interpretation is directly supported by the clip.

Thinking of tangent only as a formula

Clear evidence
Supplementary explanation
Evidence
  1. Audio
    Observation

    The presenter repeatedly uses the slope of the ray rather than only symbolic manipulation.

  2. Diagram
    Observation

    Each value is justified geometrically on the unit circle.

Misconception

Students may treat tan⁡θ\tan \theta as purely an algebraic ratio and miss its geometric meaning as a slope on the unit circle.

Clarification

This clip emphasizes that tangent can be read directly from the steepness and direction of the terminal ray.

Confusing negative angle with negative magnitude only

Approximate timing
Supplementary explanation
Evidence
  1. Diagram
    Observation

    The ray for -π/4 is drawn below the x-axis.

  2. Formula
    Observation

    The table entry is -1.

Uncertainties
  1. The video does not finish the verbal explanation before the clip ends.

Misconception

Learners may think a negative angle merely flips the picture without affecting the sign of the slope.

Clarification

Here the negative angle produces a downward-sloping ray, which is why the tangent value is negative.

Mistaking early tangent points for a straight line

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 01:12.000 the speaker says, "if you just saw that you might say oh maybe it's some type of a line but we'll see very clearly it's not a line".

Misconception

After plotting only a few points, one may think the tangent graph is a line.

Clarification

The video explicitly states that the graph is not a line, and then explains unbounded growth near π/2\pi/2.

Mistaking tangent for a continuous curve through π/2π/2

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 00:00:38-00:00:42 the speaker says the function is “not quite defined right over there, we have a vertical asymptote.”

  2. Audio
    Observation

    At 00:01:19-00:01:24 the speaker says the graph “jumps back down here” after crossing π/2π/2.

  3. Diagram
    Observation

    The graph is broken by vertical dashed lines and a new branch starts separately on the other side.

Misconception

One might think the graph should continue smoothly upward past π/2π/2 instead of breaking and restarting on another branch.

Clarification

The clip explicitly marks the boundary as undefined and shows a vertical asymptote, then demonstrates that just after π/2π/2 the graph jumps to a very negative branch rather than continuing through the asymptote.

Assuming the tangent value stays positive just after π/2π/2

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 00:01:10-00:01:18 the speaker emphasizes that just after crossing π/2π/2 the slope is “hugely negative.”

  2. Diagram
    Observation

    The new branch is drawn below the x-axis to the right of the asymptote.

Misconception

Because the previous branch was rising to +∞\infty , one may expect nearby angles just beyond π/2π/2 also to give large positive tangent values.

Clarification

The unit-circle slope picture shows that immediately after π/2π/2 the ray lies in the second quadrant, so its slope is large negative, and the graph restarts from below.

Do not treat the table entries as the only usable tangent values

Clear evidence
Supplementary explanation
Evidence
  1. Audio
    Observation

    The speaker repeatedly derives new values from unit-circle geometry instead of reading only the table.

  2. Diagram
    Observation

    The unit circle is used to explain 3π/43π/4 and later angles.

Misconception

One might think tangent values can only be taken directly from the listed table rows.

Clarification

The video shows that new values such as tan⁡(3π/4)\tan (3π/4), tan⁡(π)\tan (π), and the next positive-one value are obtained by extending the unit-circle reasoning, not merely by copying the table.

An asymptote is not a plotted point on the tangent graph

Clear evidence
Supplementary explanation
Evidence
  1. Audio
    Observation

    The speaker says the slope approaches positive infinity near 3π/23π/2.

  2. Diagram
    Observation

    The graph is broken by dashed vertical lines rather than passing through them.

Misconception

A learner may imagine that the tangent graph attains a finite y-value exactly at the dashed vertical line.

Clarification

In the clip, angles such as 3π/23π/2 are shown as boundaries where the curve grows without bound and the graph is separated by dashed asymptotes, not as ordinary points on the curve.

Concept relations · 21

Goal: become familiar with the graph of y=tan⁡θy=\tan\theta → Unit-circle setup for visualizing tangent values

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says he will set up a unit circle in order to visualize tangent values for the graph of tangent.

Application
Explanation

The unit-circle construction is introduced as the tool for understanding the target graph of y=tan⁡θy=\tan\theta.

Unit-circle setup for visualizing tangent values → Angle θ\theta formed from the positive xx-axis

Clear evidence
Shown in the video
Evidence
  1. Diagram
    Observation

    The ray and angle are drawn inside the newly created coordinate system and circle.

Contains
Explanation

The unit-circle setup contains the standard-position angle representation used to locate a point on the circle.

Angle θ\theta formed from the positive xx-axis → Point on the unit circle has coordinates (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta)

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker links the ray intersecting the unit circle to the coordinates (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta).

Application
Explanation

Once the angle is drawn, the unit-circle definition assigns the intersection point the coordinates (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta).

Point on the unit circle has coordinates (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta) → Tangent identity tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}

Clear evidence
Shown in the video
Evidence
  1. Formula
    Observation

    The point label (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta) is followed by the equation tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}.

Proof dependency
Explanation

The quotient identity is interpreted through the coordinates of the unit-circle point: sine is the yy-coordinate and cosine is the xx-coordinate.

Tangent identity tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta} → Tangent as the slope of the terminal ray

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says the y-coordinate over the x-coordinate is essentially the slope of this line.

  2. Formula
    Observation

    ΔyΔx\frac{\Delta y}{\Delta x} is written alongside sin⁡θcos⁡θ\frac{\sin\theta}{\cos\theta}.

Equivalent
Explanation

Within the unit-circle picture, the algebraic ratio sin⁡θcos⁡θ\frac{\sin\theta}{\cos\theta} and the geometric slope ΔyΔx\frac{\Delta y}{\Delta x} describe the same quantity.

Tangent as the slope of the terminal ray → Transition from geometric explanation to tabulating values

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    After explaining slope, the speaker says, "So now let's make a table."

Application
Explanation

The slope interpretation motivates the next step: listing several angles and computing their tangent values for graphing.

Tangent interpreted as the slope of the terminal ray → Building a table of values before graphing

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says the chosen values will help us think about the shape of the graph of y=tan⁡θy = \tan θ.

  2. Formula
    Observation

    The table is built before any graph is drawn.

Application
Explanation

The geometric slope interpretation is converted into numerical table entries to prepare for graphing.

Using a unit-circle ray to evaluate tangent → Value of tangent at π/4π/4 radians

Clear evidence
Shown in the video
Evidence
  1. Diagram
    Observation

    Specific rays on the unit circle are used to determine the values 1 and -1.

Application
Explanation

The π/4π/4 ray on the unit circle provides the visual basis for concluding tan⁡(π/4)=1\tan(\pi/4)=1.

Tangent as sine divided by cosine → Value of tangent at π/4π/4 radians

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker explicitly invokes sine of theta over cosine of theta to explain the value 1.

Proof dependency
Explanation

The identity tan⁡θ=sin⁡θcos⁡θ\tan \theta = \frac{\sin \theta}{\cos \theta} is used to justify the special value at θ=π/4\theta=\pi/4.

Value of tangent at 0 radians → Building a table of values before graphing

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The presenter says these easy values will help form the shape of the graph.

  2. Formula
    Observation

    The first tabulated point is (0,0).

Contains
Explanation

The value tan⁡0=0\tan 0 = 0 is one of the sample points collected to infer the overall graph shape.

Value of tan⁡(−π/4)\tan(-\pi/4) → Initial plotted points for y=tan⁡θy=\tan\theta

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 00:46.000 the speaker says, "let's just start plotting a few of these points" after completing the table.

  2. Diagram
    Observation

    The plotted points correspond exactly to the table entries.

Application
Explanation

The computed tangent values are applied to create the initial graph of y=tan⁡θy=\tan\theta.

Initial plotted points for y=tan⁡θy=\tan\theta → Vertical asymptote of the tangent graph at θ=π/2\theta=\pi/2

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    At 01:12.000 the speaker contrasts the plotted points with the later claim that the graph is not a line, then discusses behavior near π/2\pi/2 through 02:00.000.

Contrast
Explanation

The finite plotted points suggest simple linear behavior, but the later limiting argument shows an asymptote instead.

Find an answer · 29

Why does the lesson introduce a unit circle before graphing y=tan⁡θy=\tan\theta?

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says he sets up a unit circle so we can visualize what the tangent of various thetas are.

Knowledge points
  1. Goal: become familiar with the graph of y=tan⁡θy=\tan\theta
  2. Unit-circle setup for visualizing tangent values

What are the coordinates of the point where the terminal side of θ\theta meets the unit circle?

Clear evidence
Shown in the video
Evidence
  1. Formula
    Observation

    The point is labeled (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta).

Knowledge points
  1. Point on the unit circle has coordinates (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta)

How is tan⁡θ\tan\theta defined in terms of sine and cosine in this clip?

Clear evidence
Shown in the video
Evidence
  1. Formula
    Observation

    The equation tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta} is written on screen.

Knowledge points
  1. Tangent identity tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta}

Why can tangent be interpreted as the slope of the ray from the origin?

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says the ratio is essentially the slope of the line, change in y over change in x.

Knowledge points
  1. Tangent as the slope of the terminal ray
  2. Deriving the slope interpretation of tangent from the unit circle

Which coordinate is cosine and which is sine on the unit circle?

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker corrects an initial slip and states that the x-coordinate is cosine theta.

Knowledge points
  1. Point on the unit circle has coordinates (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta)
  2. Do not swap the unit-circle coordinates

What does the instructor do after explaining tangent geometrically?

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says, "So now let's make a table."

Knowledge points
  1. Transition from geometric explanation to tabulating values

Why does the video say tan⁡0=0\tan 0 = 0?

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker asks what is the slope of this ray when theta is zero radians and answers that it is zero.

Knowledge points
  1. Value of tangent at 0 radians
  2. Tangent interpreted as the slope of the terminal ray

How is tan⁡(π/4)=1\tan (π/4)=1 derived from the unit circle?

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker explains that at π/4π/4 the x-coordinate and y-coordinate are the same, so the slope is 1.

Knowledge points
  1. Value of tangent at π/4π/4 radians
  2. Tangent as sine divided by cosine
  3. Tangent interpreted as the slope of the terminal ray

What tangent value is assigned to -π/4 in this segment?

Clear evidence
Shown in the video
Evidence
  1. Formula
    Observation

    The table records -π/4 with tangent -1.

  2. Diagram
    Observation

    A fourth-quadrant ray is drawn for the negative angle.

Uncertainties
  1. The verbal explanation is incomplete at the end of the clip.

Knowledge points
  1. Value of tangent at -π/4 radians
  2. Tangent interpreted as the slope of the terminal ray

Why build a table of θ and tan θ before drawing the graph?

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says he is picking values that will help us think about the shape of the graph of y=tan⁡θy = \tan θ.

Knowledge points
  1. Building a table of values before graphing

Where does the video use sin⁡θ/cos⁡θ\sin θ / \cos θ to explain a tangent value?

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The speaker says tangent of theta is sine of theta over cosine of theta, and they are the same thing at this angle.

Knowledge points
  1. Tangent as sine divided by cosine
  2. Value of tangent at π/4π/4 radians

How does the video compute tan⁡(−π/4)\tan(-\pi/4) from the unit circle?

Clear evidence
Shown in the video
Evidence
  1. Audio
    Observation

    The full explanation of tan⁡(−π/4)\tan(-\pi/4) occurs from 00:00.000 to 00:45.000.

Knowledge points
  1. Tangent as sine divided by cosine
  2. Value of tan⁡(−π/4)\tan(-\pi/4)
Coverage and review notes

Covered · Opening statement of purpose and visible title y=tan⁡θy=\tan\theta.

Covered · Auxiliary axes and unit circle are drawn to visualize tangent values.

Covered · A ray from the origin defines angle θ\theta in standard position.

Covered · The intersection point is labeled (cos⁡θ,sin⁡θ)(\cos\theta,\sin\theta), with an audible self-correction.

Covered · The quotient identity tan⁡θ=sin⁡θcos⁡θ\tan\theta=\frac{\sin\theta}{\cos\theta} is stated and written.

Covered · The ratio is reinterpreted as the slope ΔyΔx\frac{\Delta y}{\Delta x} of the terminal ray.

Covered · The diagram is simplified and a new table is begun, but no entries are completed within the clip.

Covered · Opening setup shows the title y=tan⁡θy = \tan θ, the blank table, the unit circle, and the empty coordinate grid.

Covered · The presenter evaluates θ=0θ = 0 by noting the ray is horizontal and therefore has slope 0.

Covered · The speaker explains the strategy of choosing easy angles to infer the shape of the graph.

Covered · The angle π/4π/4 is introduced, drawn on the unit circle, and justified as having tangent 1 through equal coordinates and sin⁡/cos⁡\sin /\cos equality.

Covered · The angle -π/4 is introduced and written in the table with tangent -1; the spoken explanation begins but the clip ends before it is fully developed.

Covered · Unit-circle coordinates for −π/4-\pi/4 are explained and used to compute tan⁡(−π/4)=−1\tan(-\pi/4)=-1.

Covered · The unit circle is cleaned up and the table entry for −π/4-\pi/4 is finalized as −1-1.

Covered · The graph axes are identified and the first three points of y=tan⁡θy=\tan\theta are plotted.

Covered · The speaker warns the graph is not a line, explains growth toward infinity near π/2\pi/2, and draws a vertical asymptote.

Covered · Initial layout and setup for the tangent graph are visible; the spoken content in this opening portion is fragmentary, but it leads directly into the slope-based explanation.

Covered · The speaker explains unbounded positive and negative slope behavior near ±π/2π/2 while the central branch is drawn.

Covered · The clip explicitly identifies a vertical asymptote and completes the central branch between -π/2 and π/2π/2.

Covered · The instructor continues past π/2π/2, explaining why the next branch starts from very negative values and rises again.

Covered · A concrete example angle 3π/43π/4 is introduced and rewritten as π/2+π/4π/2 + π/4, though the example is not completed within the clip.

Covered · The entire supplied clip is a continuous whiteboard explanation of tangent values, unit-circle slopes, plotted points, asymptotes, and periodic repetition.

Covered · The entire clip focuses on introducing the shape and periodic nature of the tangent graph.

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