Math Problem Statement

Evaluate the indefinite integral using Substitution: ∫ 8x^5 cos(4x^6) dx

Solution

Let's solve the given integral step by step. The integral is:

8x5cos(4x6)dx\int 8x^5 \cos(4x^6) \, dx

Step 1: Substitution

Let u=4x6u = 4x^6. Then, differentiate uu with respect to xx: dudx=24x5ordu=24x5dx\frac{du}{dx} = 24x^5 \quad \text{or} \quad du = 24x^5 \, dx

From this, solve for x5dxx^5 \, dx: x5dx=124dux^5 \, dx = \frac{1}{24} du

Step 2: Rewrite the Integral

Substitute u=4x6u = 4x^6 and x5dx=124dux^5 \, dx = \frac{1}{24} du into the integral: 8x5cos(4x6)dx=8124cos(u)du\int 8x^5 \cos(4x^6) \, dx = \int 8 \cdot \frac{1}{24} \cos(u) \, du

Simplify the constants: 8x5cos(4x6)dx=824cos(u)du=13cos(u)du\int 8x^5 \cos(4x^6) \, dx = \frac{8}{24} \int \cos(u) \, du = \frac{1}{3} \int \cos(u) \, du

Step 3: Integrate

The integral of cos(u)\cos(u) is sin(u)\sin(u): 13cos(u)du=13sin(u)+C\frac{1}{3} \int \cos(u) \, du = \frac{1}{3} \sin(u) + C

Step 4: Substitute Back u=4x6u = 4x^6

Replace uu with 4x64x^6 to return to the original variable: 13sin(u)+C=13sin(4x6)+C\frac{1}{3} \sin(u) + C = \frac{1}{3} \sin(4x^6) + C

Final Answer:

8x5cos(4x6)dx=13sin(4x6)+C\int 8x^5 \cos(4x^6) \, dx = \frac{1}{3} \sin(4x^6) + C

Would you like further clarifications or detailed explanations of any step?


Related Questions:

  1. What is the general method of substitution in integration?
  2. How do you handle integrals with trigonometric functions?
  3. Can substitution work for definite integrals? How?
  4. What are other strategies for solving integrals that cannot use substitution?
  5. How does the chain rule in differentiation relate to substitution in integration?

Tip:

When solving integrals using substitution, always verify by differentiating your result to check if it matches the original integrand.

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Math Problem Analysis

Mathematical Concepts

Calculus
Integration
Trigonometric Functions
Substitution Method

Formulas

∫ cos(u) du = sin(u) + C

Theorems

Substitution Rule in Integration

Suitable Grade Level

Grades 11-12 or Early College