Skip to content
START WITH A QUESTION

What would you like to understand?

Find an answer. See the moment it becomes clear. Follow the idea further.

← Concept directory

Answers for “为什么 f(0) 等于 1?”

9 keyword matches

Understanding your question. You can explore the search results below now.

Meet the concept

↗

The coefficient formula for a Maclaurin series is cn=f(n)(0)/nc_n = f^{(n)}(0) / n!. This means the nth coefficient of the power series is found by taking the nth derivative of the function, evaluating it at x=0x=0, and dividing by n factorial.

Conditions: The series is expanded around x=0x=0.; The function must have derivatives up to order n at 0 for the displayed formula to make sense.; The function is assumed to have a power series representation.

Meet the concept

↗

In this forecasting method, α\alpha is the smoothing constant that determines the weight assigned to the most recent actual demand. The term (1−α)(1-\alpha) is the complementary weight applied to the previous forecast.

Conditions: α\alpha is fixed at 0.4 in the worked example.; (1−α)(1-\alpha) is calculated as 0.6.; The weights must sum to 1 for the formula to represent a valid weighted average.

Meet the concept

↗

If no forecast value for the first period is given, the standard assumption is to set the first forecast equal to the first actual value, expressed as F1=A1F_1 = A_1. This provides a starting point for the exponential smoothing calculations.

Conditions: No initial forecast value is provided for the first period.; You are beginning an exponential smoothing calculation.

Meet the concept

↗

The rectangular pulse function, denoted as f(t)f(t), is defined piecewise. It takes the value 1 when the absolute value of tt is less than or equal to 1 (i.e., ∣t∣≤1|t| \le 1), and it takes the value 0 for all other values of tt (i.e., ∣t∣>1|t| > 1).

Conditions: tt is a real number.; The function is defined on the entire real line.

Meet the concept

↗

The value of the definite integral from 0 to 7 is 10.5. This is obtained by summing the signed areas of the three sub-intervals created by splitting at the breakpoints: 4.5, 6, and 0.

Conditions: The function is piecewise-linear.; The integration interval is from 0 to 7.; The graph consists of regions with signed areas 4.5, 6, and 0.

Meet the concept

↗

The steps involve finding the potential function F(x,y)F(x,y) by integrating M with respect to x and N with respect to y, then combining the results to form the implicit solution F(x,y)=CF(x,y) = C.

Conditions: The differential equation has been verified as exact.

Meet the concept

↗

The critical parameter value is approximately C* = 3.079. Below this value (C<CC < C*), the differential equation has three equilibria.

Conditions: The differential equation is dz/dt=4z−z3+Cdz/dt = 4z - z^3 + C.; C* is the threshold where the number of real roots of 4z−z3+C=04z - z^3 + C = 0 changes.

Meet the concept

↗

The video presents the single-parameter exponential smoothing update rule. The new forecast equals the prior forecast plus a fraction alpha of the prior forecast error, where the error is measured as actual minus forecast from the previous period.

Conditions: Used recursively over discrete time periods.; Requires a starting forecast value.; In the example, alpha is supplied as 0.2.

Meet the concept

↗

The Maclaurin series for the cosine function is the infinite power series cos⁡x=1−x22!+x44!−x66!+…\cos x = 1 - \frac{x^2}{2!} + \frac{x^4}{4!} - \frac{x^6}{6!} + \ldots, which can be written in summation notation as ∑k=0∞(−1)kx2k(2k)!\sum_{k=0}^{\infty}\frac{(-1)^k x^{2k}}{(2k)!}. The video reveals that the specific series-defined function f(x)f(x) is exactly equivalent to cos⁡x\cos x for all real numbers.

Conditions: The variable xx is a real number.; The series is evaluated at x=0x=0 (Maclaurin series).