Math Problem Statement

Evaluate limx→0 xcotx.

Solution

To evaluate the limit of xcot(x)x \cot(x) as x0x \to 0, we proceed as follows:

We know that: cot(x)=cos(x)sin(x)\cot(x) = \frac{\cos(x)}{\sin(x)}

Thus, the expression xcot(x)x \cot(x) becomes: xcot(x)=xcos(x)sin(x)=xcos(x)sin(x)x \cot(x) = x \cdot \frac{\cos(x)}{\sin(x)} = \frac{x \cos(x)}{\sin(x)}

Now, we evaluate the limit: limx0xcos(x)sin(x)\lim_{x \to 0} \frac{x \cos(x)}{\sin(x)}

We can split this into two parts: limx0xsin(x)limx0cos(x)\lim_{x \to 0} \frac{x}{\sin(x)} \cdot \lim_{x \to 0} \cos(x)

From the standard limit, we know: limx0xsin(x)=1\lim_{x \to 0} \frac{x}{\sin(x)} = 1 and limx0cos(x)=1\lim_{x \to 0} \cos(x) = 1

Therefore: limx0xcot(x)=11=1\lim_{x \to 0} x \cot(x) = 1 \cdot 1 = 1

So, the value of the limit is: 1\boxed{1}

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Related questions:

  1. How do you evaluate limits involving trigonometric functions in general?
  2. What is L'Hopital's Rule, and can it be used for this limit?
  3. How do small-angle approximations help in limit evaluations?
  4. What is the limit limx0sin(x)x\lim_{x \to 0} \frac{\sin(x)}{x}, and why is it important?
  5. How does the continuity of cosine and sine functions affect their limits?

Tip: Remember that limx0sin(x)x=1\lim_{x \to 0} \frac{\sin(x)}{x} = 1 is a crucial result for evaluating many trigonometric limits.

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Math Problem Analysis

Mathematical Concepts

Limits
Trigonometry

Formulas

cot(x) = cos(x)/sin(x)
lim x → 0 (sin(x)/x) = 1

Theorems

Standard trigonometric limits
Continuity of trigonometric functions

Suitable Grade Level

Grades 10-12