Math Problem Statement

Find the limit of (sin(3x^2)cos(5x))/(2x^2) as x approaches 0.

Solution

The problem you've presented involves finding the limit:

limx0sin(3x2)cos(5x)2x2\lim_{{x \to 0}} \frac{\sin(3x^2)\cos(5x)}{2x^2}

To solve this limit, we will use the small-angle approximations for sine and cosine functions and the limit properties.

Step 1: Use small-angle approximations

For small values of xx, sin(x)x\sin(x) \approx x and cos(x)1\cos(x) \approx 1. Therefore, for small values of 3x23x^2 and 5x5x, sin(3x2)3x2andcos(5x)1\sin(3x^2) \approx 3x^2 \quad \text{and} \quad \cos(5x) \approx 1

Step 2: Substitute and simplify

Substituting these approximations into the limit gives: limx03x212x2=limx03x22x2=limx032=32\lim_{{x \to 0}} \frac{3x^2 \cdot 1}{2x^2} = \lim_{{x \to 0}} \frac{3x^2}{2x^2} = \lim_{{x \to 0}} \frac{3}{2} = \frac{3}{2}

Hence, the limit is 32\frac{3}{2}.

Do you have any further questions on this, or is there another problem you need help with? Here are a few related questions you might find interesting:

  1. How would the solution change if the cosine term was cos(5x2)\cos(5x^2) instead?
  2. What happens to the limit if the denominator was x3x^3 instead of 2x22x^2?
  3. Can you apply L'Hopital's Rule to solve this limit? If yes, how?
  4. How does the limit behave if xx approaches a different value, say π\pi?
  5. What role do the coefficients 3 and 5 play in the behavior of the limit?

Tip: Always check if a function behaves nicely around the limit point (like being continuous and differentiable) before applying L'Hopital’s rule, as it requires both the numerator and denominator to be differentiable.

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Math Problem Analysis

Mathematical Concepts

Limits
Trigonometry
Small-Angle Approximation

Formulas

sin(x) ≈ x for small x
cos(x) ≈ 1 for small x

Theorems

Small-Angle Approximation
Limit Theorem

Suitable Grade Level

Grades 11-12 or College Calculus