Math Problem Statement

Evaluate the limit lim sin(x) x→0 sin²(x)-2tan(x)

Solution

To evaluate the limit limx0sin(x)sin2(x)2tan(x)\lim_{{x \to 0}} \frac{\sin(x)}{\sin^2(x) - 2\tan(x)}, we need to simplify and analyze the expression as xx approaches 0.

First, let's recall the small-angle approximations for sine and tangent functions:

  • sin(x)x\sin(x) \approx x
  • tan(x)x\tan(x) \approx x

Let's rewrite the expression using these approximations: sin2(x)x2and2tan(x)2x\sin^2(x) \approx x^2 \quad \text{and} \quad 2\tan(x) \approx 2x

So, the expression inside the limit becomes: sin(x)sin2(x)2tan(x)xx22x\frac{\sin(x)}{\sin^2(x) - 2\tan(x)} \approx \frac{x}{x^2 - 2x}

Simplify the denominator: x22x=x(x2)x^2 - 2x = x(x - 2)

Thus, the limit expression can be rewritten as: xx(x2)=xx22x\frac{x}{x(x - 2)} = \frac{x}{x^2 - 2x}

We can cancel the common factor xx in the numerator and the denominator: xx(x2)=1x2\frac{x}{x(x - 2)} = \frac{1}{x - 2}

Now, we need to evaluate the limit: limx01x2\lim_{{x \to 0}} \frac{1}{x - 2}

Substitute x=0x = 0: 102=12=12\frac{1}{0 - 2} = \frac{1}{-2} = -\frac{1}{2}

Therefore, the limit is: 12\boxed{-\frac{1}{2}}

Do you have any questions or need more details?

Here are some related questions to further explore the topic:

  1. What is the small-angle approximation for cos(x)\cos(x)?
  2. How does L'Hôpital's Rule apply to limits involving indeterminate forms?
  3. Can you provide an example where L'Hôpital's Rule is necessary to evaluate a limit?
  4. What are the different types of indeterminate forms?
  5. How do Taylor series expansions help in evaluating limits?
  6. What is the difference between limx0sin(x)x\lim_{{x \to 0}} \frac{\sin(x)}{x} and limx0xsin(x)\lim_{{x \to 0}} \frac{x}{\sin(x)}?
  7. How can we use series expansions to approximate tan(x)\tan(x) for small angles?
  8. What is the importance of knowing the behavior of trigonometric functions near 0?

Tip: Always check if the limit results in an indeterminate form (like 00\frac{0}{0} or \frac{\infty}{\infty}) before simplifying or applying L'Hôpital's Rule.

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Math Problem Analysis

Mathematical Concepts

Limits
Trigonometric Functions
Small-angle Approximations

Formulas

Small-angle approximations for sine and tangent

Theorems

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Suitable Grade Level

Advanced High School and College