Math Problem Statement

Evaluate lim x → 0

sin ( 2 x ) tan ( − 10 x ) .

Solution

We are asked to evaluate the limit:

limx0sin(2x)tan(10x)\lim_{x \to 0} \sin(2x) \cdot \tan(-10x)

Let's break it down step by step.

Step 1: Simplify the Trigonometric Functions

  1. The sine function is: sin(2x)\sin(2x) As xx approaches 0, 2x2x also approaches 0. We know from the small angle approximation that: sin(2x)2x as x0\sin(2x) \approx 2x \text{ as } x \to 0

  2. The tangent function is: tan(10x)\tan(-10x) As xx approaches 0, 10x-10x also approaches 0. We also know from the small angle approximation that: tan(10x)10x as x0\tan(-10x) \approx -10x \text{ as } x \to 0

Step 2: Substitute the Approximations into the Limit

Using these approximations: limx0sin(2x)tan(10x)limx0(2x)(10x)\lim_{x \to 0} \sin(2x) \cdot \tan(-10x) \approx \lim_{x \to 0} (2x) \cdot (-10x)

Step 3: Simplify the Expression

limx0(2x)(10x)=limx0(20x2)\lim_{x \to 0} (2x) \cdot (-10x) = \lim_{x \to 0} (-20x^2)

Step 4: Evaluate the Limit

Now, we can evaluate the limit: limx020x2=2002=0\lim_{x \to 0} -20x^2 = -20 \cdot 0^2 = 0

Thus, the limit is:

0\boxed{0}

Would you like further details or have any questions?

Related Questions:

  1. How do we derive the small angle approximations for sine and tangent?
  2. What happens if we use higher-order approximations for the sine and tangent functions?
  3. Can this limit be solved using L'Hôpital's rule?
  4. What is the geometric interpretation of this limit?
  5. How does this problem change if we consider limits as xx approaches infinity?

Tip: When dealing with trigonometric limits as xx approaches 0, small angle approximations can greatly simplify the problem.

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Math Problem Analysis

Mathematical Concepts

Limits
Trigonometry

Formulas

Small angle approximations

Theorems

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Suitable Grade Level

Advanced High School