Math Problem Statement

Let's evaluate the following limit: lim (sin(πx) / (x - 1)) as x approaches 1. Can L'Hopital's rule be used to evaluate the limit?

Solution

Let's break down the problem shown in the image step by step.

Given:

You are asked to evaluate the limit: limx1sin(πx)x1\lim_{x \to 1} \frac{\sin(\pi x)}{x - 1}

Step 1: Checking if L'Hopital's Rule can be applied

L'Hopital's Rule can be applied when a limit results in an indeterminate form of 00\frac{0}{0} or \frac{\infty}{\infty}.

  1. Substitute x=1x = 1 into the expression:
    • The numerator becomes sin(π1)=sin(π)=0\sin(\pi \cdot 1) = \sin(\pi) = 0.
    • The denominator is 11=01 - 1 = 0.

Thus, the limit is of the indeterminate form 00\frac{0}{0}, so Yes, L'Hopital's Rule can be applied.

Step 2: Differentiating the numerator and denominator

L'Hopital's Rule states that we can take the derivative of the numerator and the derivative of the denominator, and then re-evaluate the limit.

  1. Derivative of the numerator: ddxsin(πx)=πcos(πx)\frac{d}{dx} \sin(\pi x) = \pi \cos(\pi x)
  2. Derivative of the denominator: ddx(x1)=1\frac{d}{dx} (x - 1) = 1

Step 3: Applying the limit after differentiation

Now, the limit becomes: limx1πcos(πx)1\lim_{x \to 1} \frac{\pi \cos(\pi x)}{1} Substitute x=1x = 1: πcos(π1)=πcos(π)=π(1)=π\pi \cos(\pi \cdot 1) = \pi \cos(\pi) = \pi \cdot (-1) = -\pi

Final Answer:

The limit evaluates to π-\pi.

Summary:

  1. Can L'Hopital's rule be used? Yes.
  2. What is the indeterminate form? 00\frac{0}{0}.
  3. Final answer: π-\pi.

Would you like any further clarification?

Here are five related questions to explore:

  1. What are the conditions for using L'Hopital's Rule?
  2. How can you handle limits where L'Hopital’s Rule does not apply?
  3. What other indeterminate forms exist apart from 00\frac{0}{0}?
  4. How do you differentiate trigonometric functions effectively?
  5. What happens if you apply L'Hopital's Rule multiple times?

Tip: Always verify whether a limit results in an indeterminate form before applying L'Hopital's Rule.

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Math Problem Analysis

Mathematical Concepts

Calculus
Limits
L'Hopital's Rule

Formulas

L'Hopital's Rule: If lim f(x)/g(x) results in an indeterminate form like 0/0 or ∞/∞, then lim f(x)/g(x) = lim f'(x)/g'(x) (if the limit on the right-hand side exists).
sin(πx) differentiation: d/dx [sin(πx)] = πcos(πx)

Theorems

L'Hopital's Rule

Suitable Grade Level

Grades 11-12, College Calculus