Math Problem Statement

Вычислить используя правило Лопиталя

Вычислить используя правило Лопиталя

Solution

To solve the given limit using L'Hôpital's rule:

We are tasked to compute:

limxln(1+2x)π2arctan(x).\lim_{x \to \infty} \frac{\ln\left(1 + \frac{2}{x}\right)}{\pi - 2\arctan(x)}.

Step 1: Analyze the behavior of the numerator and denominator

  • Numerator: As xx \to \infty, 2x0\frac{2}{x} \to 0, so ln(1+2x)ln(1)=0\ln\left(1 + \frac{2}{x}\right) \to \ln(1) = 0.
  • Denominator: As xx \to \infty, arctan(x)π2\arctan(x) \to \frac{\pi}{2}, so π2arctan(x)ππ=0\pi - 2\arctan(x) \to \pi - \pi = 0.

Thus, the limit is in an indeterminate form 00\frac{0}{0}, and we can apply L'Hôpital's rule.


Step 2: Differentiate numerator and denominator

  • Derivative of the numerator: ddxln(1+2x)=11+2x(2x2)=2x21+2x.\frac{d}{dx} \ln\left(1 + \frac{2}{x}\right) = \frac{1}{1 + \frac{2}{x}} \cdot \left(-\frac{2}{x^2}\right) = \frac{-\frac{2}{x^2}}{1 + \frac{2}{x}}.

  • Derivative of the denominator: ddx(π2arctan(x))=211+x2.\frac{d}{dx} \left(\pi - 2\arctan(x)\right) = -2 \cdot \frac{1}{1 + x^2}.


Step 3: Rewrite the new fraction

The limit becomes: limx2x21+2x21+x2.\lim_{x \to \infty} \frac{\frac{-\frac{2}{x^2}}{1 + \frac{2}{x}}}{-\frac{2}{1 + x^2}}.

Simplify: =limx2x2(1+2x)21+x2.= \lim_{x \to \infty} \frac{\frac{2}{x^2(1 + \frac{2}{x})}}{\frac{2}{1 + x^2}}.

Cancel the factor of 2: =limx1x2(1+2x)11+x2.= \lim_{x \to \infty} \frac{\frac{1}{x^2(1 + \frac{2}{x})}}{\frac{1}{1 + x^2}}.

Simplify further: =limx1+x2x2(1+2x).= \lim_{x \to \infty} \frac{1 + x^2}{x^2\left(1 + \frac{2}{x}\right)}.


Step 4: Evaluate the limit as xx \to \infty

As xx \to \infty:

  • 1+x2x21 + x^2 \to x^2,
  • 1+2x11 + \frac{2}{x} \to 1.

Thus: limx1+x2x2(1+2x)=limxx2x2=1.\lim_{x \to \infty} \frac{1 + x^2}{x^2\left(1 + \frac{2}{x}\right)} = \lim_{x \to \infty} \frac{x^2}{x^2} = 1.


Final Answer:

1.\boxed{1}.


Would you like me to clarify any step or go deeper into the explanation? Here are 5 related questions for further exploration:

  1. What is the general procedure to apply L'Hôpital's rule to indeterminate forms?
  2. How do the properties of logarithmic functions help simplify limits?
  3. Can you extend this problem to a similar one involving arcsin(x)\arcsin(x) or arccos(x)\arccos(x)?
  4. What happens if the numerator and denominator approach infinity instead of zero?
  5. How does arctan(x)\arctan(x) behave as xx \to -\infty?

Tip: Always check whether a limit is indeterminate before applying L’Hôpital’s rule to ensure it is valid!

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Limits
Logarithmic Functions
Inverse Trigonometric Functions
L'Hôpital's Rule

Formulas

L'Hôpital's Rule: lim (f(x)/g(x)) = lim (f'(x)/g'(x)) when indeterminate
Derivative of ln(1 + u): d/dx[ln(1 + u)] = u' / (1 + u)
Derivative of arctan(x): d/dx[arctan(x)] = 1 / (1 + x^2)

Theorems

L'Hôpital's Rule

Suitable Grade Level

Undergraduate Calculus