Math Problem Statement

Evaluate the limit \( \lim_{{x \to \frac{\pi}{3}}} \frac{\sqrt{3} \cos x - \sin x}{x - \frac{\pi}{3}} \)

Solution

The problem presented is to evaluate the limit:

limxπ33cosxsinxxπ3\lim_{{x \to \frac{\pi}{3}}} \frac{\sqrt{3} \cos x - \sin x}{x - \frac{\pi}{3}}

To solve this, we can proceed by substituting values or by using L'Hôpital's Rule because the direct substitution results in an indeterminate form of 00\frac{0}{0}. Here's the step-by-step solution:

  1. Substitute x=π3x = \frac{\pi}{3}: 3cos(π3)sin(π3)=31232=0\sqrt{3} \cos \left(\frac{\pi}{3}\right) - \sin \left(\frac{\pi}{3}\right) = \sqrt{3} \cdot \frac{1}{2} - \frac{\sqrt{3}}{2} = 0 xπ3=0x - \frac{\pi}{3} = 0 So, this substitution yields 00\frac{0}{0}, an indeterminate form.

  2. Apply L'Hôpital's Rule: Differentiate the numerator and the denominator with respect to xx:

    • Numerator: ddx(3cosxsinx)=3sinxcosx\frac{d}{dx}(\sqrt{3} \cos x - \sin x) = -\sqrt{3} \sin x - \cos x
    • Denominator: ddx(xπ3)=1\frac{d}{dx}(x - \frac{\pi}{3}) = 1

    So, the limit now becomes: limxπ33sinxcosx\lim_{{x \to \frac{\pi}{3}}} -\sqrt{3} \sin x - \cos x

  3. Substitute x=π3x = \frac{\pi}{3} into the new expression: 3sin(π3)cos(π3)=33212-\sqrt{3} \sin \left(\frac{\pi}{3}\right) - \cos \left(\frac{\pi}{3}\right) = -\sqrt{3} \cdot \frac{\sqrt{3}}{2} - \frac{1}{2} =3212=2= -\frac{3}{2} - \frac{1}{2} = -2

Therefore, the value of the limit is:

2\boxed{-2}

Would you like further details on any of the steps or additional information on limit calculations?

Here are five related questions for further exploration:

  1. What is L'Hôpital's Rule and when can it be applied?
  2. How do you identify an indeterminate form in limits?
  3. What are other methods to solve limits besides L'Hôpital's Rule?
  4. How do trigonometric limits differ from polynomial limits?
  5. How do you handle limits approaching infinity in trigonometric functions?

Tip: When solving limits, always check for an indeterminate form before applying L'Hôpital's Rule.

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Math Problem Analysis

Mathematical Concepts

Limits
Trigonometry
Indeterminate Forms

Formulas

L'Hôpital's Rule: If \( \lim_{x \to c} \frac{f(x)}{g(x)} = \frac{0}{0} \) or \( \frac{\pm \infty}{\pm \infty} \), then \( \lim_{x \to c} \frac{f(x)}{g(x)} = \lim_{x \to c} \frac{f'(x)}{g'(x)} \) provided the limit on the right exists.
Trigonometric values: \( \cos \frac{\pi}{3} = \frac{1}{2} \), \( \sin \frac{\pi}{3} = \frac{\sqrt{3}}{2} \)

Theorems

L'Hôpital's Rule

Suitable Grade Level

Grades 11-12