Math Problem Statement

Evaluate the integral \( \int \sin^2(2x) \, dx \).

Solution

To evaluate the integral

sin2(2x)dx\int \sin^2(2x) \, dx

we can use the trigonometric identity to simplify sin2(2x)\sin^2(2x). The identity is:

sin2(θ)=1cos(2θ)2\sin^2(\theta) = \frac{1 - \cos(2\theta)}{2}

Applying this identity with θ=2x\theta = 2x:

sin2(2x)=1cos(4x)2\sin^2(2x) = \frac{1 - \cos(4x)}{2}

Now the integral becomes:

sin2(2x)dx=1cos(4x)2dx\int \sin^2(2x) \, dx = \int \frac{1 - \cos(4x)}{2} \, dx

This can be split into two integrals:

=121dx12cos(4x)dx= \frac{1}{2} \int 1 \, dx - \frac{1}{2} \int \cos(4x) \, dx

Evaluating each part separately:

  1. For 121dx\frac{1}{2} \int 1 \, dx:

    121dx=12x\frac{1}{2} \int 1 \, dx = \frac{1}{2} x

  2. For 12cos(4x)dx-\frac{1}{2} \int \cos(4x) \, dx:

    We need to integrate cos(4x)\cos(4x), which gives:

    cos(4x)dx=sin(4x)4\int \cos(4x) \, dx = \frac{\sin(4x)}{4}

    Therefore:

    12cos(4x)dx=12sin(4x)4=sin(4x)8-\frac{1}{2} \int \cos(4x) \, dx = -\frac{1}{2} \cdot \frac{\sin(4x)}{4} = -\frac{\sin(4x)}{8}

Combining these results, we get:

sin2(2x)dx=12xsin(4x)8+C\int \sin^2(2x) \, dx = \frac{1}{2} x - \frac{\sin(4x)}{8} + C

where CC is the constant of integration.

Would you like further explanation on any steps?


Here are some related questions for further exploration:

  1. How would the solution change if the integrand were sin2(3x)\sin^2(3x) instead?
  2. Can you evaluate cos2(2x)dx\int \cos^2(2x) \, dx using a similar approach?
  3. How does the identity sin2(x)=1cos(2x)2\sin^2(x) = \frac{1 - \cos(2x)}{2} help simplify integrals of trigonometric squares?
  4. What happens if you use a different trigonometric identity for sin2(2x)\sin^2(2x)?
  5. How would this integral look if we had sin2(2x)exdx\int \sin^2(2x) e^x \, dx?

Tip: Always consider using trigonometric identities for powers of sine and cosine; they often simplify integrals substantially.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Trigonometric Integration
Integral of Trigonometric Functions
Trigonometric Identities

Formulas

\( \sin^2(\theta) = \frac{1 - \cos(2\theta)}{2} \)

Theorems

Trigonometric Power Reduction Identity

Suitable Grade Level

Grades 11-12