Math Problem Statement

Using derivatives to calculate the following limits: 1) \( \lim_{{x \to 1}} \frac{(x+2)^{2018} - 1}{x + 1} \) 2) \( \lim_{{x \to \frac{\pi}{6}}} \frac{2 \sin x - 1}{x - \frac{\pi}{6}} \)

Solution

Let's analyze and solve each of these limits using derivatives, as suggested by the exercise instructions.

Problem 1:

limx1(x+2)20181x+1\lim_{{x \to 1}} \frac{(x+2)^{2018} - 1}{x + 1}

This problem involves the limit of a fraction. To solve it, we can use L'Hôpital's Rule, since substituting x=1x = 1 directly gives the indeterminate form 00\frac{0}{0}.

Let's apply L'Hôpital's Rule, which requires us to take the derivative of the numerator and the denominator:

  1. Numerator Derivative: The function in the numerator is f(x)=(x+2)20181f(x) = (x+2)^{2018} - 1. The derivative f(x)f'(x) is: f(x)=2018(x+2)2017f'(x) = 2018 \cdot (x+2)^{2017}

  2. Denominator Derivative: The denominator is g(x)=x+1g(x) = x + 1, and its derivative g(x)g'(x) is: g(x)=1g'(x) = 1

After taking the derivatives, the limit becomes: limx12018(x+2)20171=2018(1+2)2017=201832017\lim_{{x \to 1}} \frac{2018 \cdot (x+2)^{2017}}{1} = 2018 \cdot (1+2)^{2017} = 2018 \cdot 3^{2017}

So, the solution to the first limit is: limx1(x+2)20181x+1=201832017\lim_{{x \to 1}} \frac{(x+2)^{2018} - 1}{x + 1} = 2018 \cdot 3^{2017}

Problem 2:

limxπ62sinx1xπ6\lim_{{x \to \frac{\pi}{6}}} \frac{2 \sin x - 1}{x - \frac{\pi}{6}}

Similar to Problem 1, substituting x=π6x = \frac{\pi}{6} directly in this limit also yields an indeterminate form 00\frac{0}{0}. We can again apply L'Hôpital's Rule:

  1. Numerator Derivative: The function in the numerator is f(x)=2sinx1f(x) = 2 \sin x - 1. Its derivative is: f(x)=2cosxf'(x) = 2 \cos x

  2. Denominator Derivative: The denominator g(x)=xπ6g(x) = x - \frac{\pi}{6} has a derivative of: g(x)=1g'(x) = 1

With L'Hôpital's Rule applied, the limit simplifies to: limxπ62cosx1=2cosπ6=232=3\lim_{{x \to \frac{\pi}{6}}} \frac{2 \cos x}{1} = 2 \cos \frac{\pi}{6} = 2 \cdot \frac{\sqrt{3}}{2} = \sqrt{3}

Thus, the solution to the second limit is: limxπ62sinx1xπ6=3\lim_{{x \to \frac{\pi}{6}}} \frac{2 \sin x - 1}{x - \frac{\pi}{6}} = \sqrt{3}

Summary of Answers:

  1. limx1(x+2)20181x+1=201832017\lim_{{x \to 1}} \frac{(x+2)^{2018} - 1}{x + 1} = 2018 \cdot 3^{2017}
  2. limxπ62sinx1xπ6=3\lim_{{x \to \frac{\pi}{6}}} \frac{2 \sin x - 1}{x - \frac{\pi}{6}} = \sqrt{3}

Would you like a more detailed explanation of each step, or do you have any questions?

Related Questions:

  1. What are the conditions for applying L'Hôpital's Rule?
  2. How would the solutions change if the exponents in Problem 1 were different?
  3. Can you explain why substitution gives an indeterminate form in these problems?
  4. Are there alternative methods to solve these limits without L'Hôpital's Rule?
  5. How does the derivative of trigonometric functions affect limits?

Tip:

When approaching limits that yield 00\frac{0}{0} or \frac{\infty}{\infty}, consider L'Hôpital's Rule, but also explore factoring, simplification, or series expansion, as these might sometimes offer simpler solutions.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Limits
Derivatives
L'Hôpital's Rule
Trigonometric Functions

Formulas

L'Hôpital's Rule: \( \lim_{{x \to c}} \frac{f(x)}{g(x)} = \lim_{{x \to c}} \frac{f'(x)}{g'(x)} \) if it gives an indeterminate form
Trigonometric Derivatives: \( \frac{d}{dx} \sin(x) = \cos(x) \)

Theorems

L'Hôpital's Rule

Suitable Grade Level

Undergraduate - Calculus I or II