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What should be noted when using the important limit lim⁡(sin⁡x)/x=1\lim (\sin x)/x = 1?

When using the important limit lim⁡x→0sin⁡xx=1\lim_{x \to 0} \frac{\sin x}{x} = 1, it must be ensured that the entire expression inside the sine function is exactly identical to the denominator, and that this entire expression approaches 0. Additionally, the angle unit must be radians.

Conditions

  • The variable inside the sine function must match the denominator exactly.
  • The matched expression must approach 0.
  • Angles are in radians.

Reasoning, step by step

  1. Identify the argument of the sine function.
  2. Check if the denominator is exactly the same as the sine argument.
  3. Verify that this common expression approaches 0.
  4. Apply the limit value of 1.

Example

The video uses a red box to highlight that in sin⁡(h/2)h/2\frac{\sin(h/2)}{h/2}, the h/2h/2 inside the sine matches the h/2h/2 in the denominator, and both approach 0 as h→0h \to 0.

Common misconceptions

  • Believing that as long as the numerator is sin(some expression) and the denominator is another expression, one can directly apply the conclusion that the limit is 1.
  • Forgetting that the limit does not hold if angles are in degrees.

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Answers are generated from source material and independently checked. Consult the original video or creator if something is unclear.