Math Problem Statement

Integrate (sin x)^3

Solution

To integrate (sinx)3(\sin x)^3, we can use a trigonometric identity and substitution. Here's the step-by-step solution:

Step 1: Use the trigonometric identity

We begin by using the identity: sin3x=sinx(1cos2x)\sin^3 x = \sin x (1 - \cos^2 x) So the integral becomes: sin3xdx=sinx(1cos2x)dx\int \sin^3 x \, dx = \int \sin x (1 - \cos^2 x) \, dx

Step 2: Substitution

Let u=cosxu = \cos x, which implies du=sinxdxdu = -\sin x \, dx. The integral becomes: sinx(1cos2x)dx=(1u2)du\int \sin x (1 - \cos^2 x) \, dx = -\int (1 - u^2) \, du

Step 3: Simplify and integrate

Now, integrate the expression: (1u2)du=(uu33)+C-\int (1 - u^2) \, du = -\left(u - \frac{u^3}{3}\right) + C

Step 4: Substitute back u=cosxu = \cos x

Now, substitute back u=cosxu = \cos x: (cosxcos3x3)+C-(\cos x - \frac{\cos^3 x}{3}) + C which simplifies to: cos3x3cosx+C\frac{\cos^3 x}{3} - \cos x + C

Thus, the integral of (sinx)3(\sin x)^3 is: sin3xdx=cos3x3cosx+C\int \sin^3 x \, dx = \frac{\cos^3 x}{3} - \cos x + C

Would you like more details on any step or have any questions?

Here are 5 related questions to extend your understanding:

  1. How would you integrate sin5x\sin^5 x?
  2. What if you were to integrate (cosx)3(\cos x)^3?
  3. How can you use a similar method to integrate (sinx)2(\sin x)^2?
  4. What is the integral of (sinx)n(\sin x)^n for general nn?
  5. Can you derive the reduction formula for (sinx)ndx\int (\sin x)^n dx?

Tip: Trigonometric identities are very useful for simplifying integrals involving powers of sine and cosine!

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Integration
Substitution Method

Formulas

sin^3 x = sin x (1 - cos^2 x)
Substitution: u = cos x, du = -sin x dx

Theorems

Trigonometric Identity

Suitable Grade Level

Grades 11-12