Math Problem Statement

Evaluate the limit: \( \lim_{{x \to 0}} \frac{\tan(x) - \sin(x)}{x^3} \).

Solution

The given limit expression is:

limx0tan(x)sin(x)x3\lim_{{x \to 0}} \frac{\tan(x) - \sin(x)}{x^3}

Step-by-Step Solution:

  1. Expand tan(x)\tan(x) and sin(x)\sin(x) using Taylor series expansions around x=0x = 0:

    • The Taylor series for tan(x)\tan(x) around 0 is: tan(x)=x+x33+O(x5)\tan(x) = x + \frac{x^3}{3} + O(x^5)
    • The Taylor series for sin(x)\sin(x) around 0 is: sin(x)=xx36+O(x5)\sin(x) = x - \frac{x^3}{6} + O(x^5)
  2. Subtract tan(x)\tan(x) and sin(x)\sin(x):

    = \frac{x^3}{3} + \frac{x^3}{6} = \frac{2x^3}{6} + \frac{x^3}{6} = \frac{x^3}{2}$$
  3. Substitute the result into the original limit: limx0tan(x)sin(x)x3=limx0x32x3=12\lim_{{x \to 0}} \frac{\tan(x) - \sin(x)}{x^3} = \lim_{{x \to 0}} \frac{\frac{x^3}{2}}{x^3} = \frac{1}{2}

Thus, the value of the limit is:

12\boxed{\frac{1}{2}}

Would you like further details on the steps?

Here are 5 related questions to expand on this concept:

  1. How are Taylor series used to approximate functions near a point?
  2. What is the Taylor series expansion of cos(x)\cos(x) around x=0x = 0?
  3. How do you handle limits involving higher powers of xx?
  4. Can you find the limit limx0sin(x)xx3\lim_{{x \to 0}} \frac{\sin(x) - x}{x^3}?
  5. What is L'Hopital's Rule, and could it be applied to solve this limit?

Tip: Taylor series expansion is very useful when working with limits, especially for small values of xx where the higher order terms can be ignored for simplification.

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Math Problem Analysis

Mathematical Concepts

Calculus
Limits
Taylor Series Expansion

Formulas

Taylor series expansion of \( \tan(x) \approx x + \frac{x^3}{3} + O(x^5) \)
Taylor series expansion of \( \sin(x) \approx x - \frac{x^3}{6} + O(x^5) \)
Subtraction of series: \( \tan(x) - \sin(x) = \frac{x^3}{2} \)

Theorems

Taylor Series
Limit Theorem

Suitable Grade Level

University Level (Calculus I)