Math Problem Statement

Evaluate the integral \( \int_{-1}^{1} x^{17} \cos^4(x) \, dx \).

Solution

The given integral is:

11x17cos4(x)dx\int_{-1}^{1} x^{17} \cos^4(x) \, dx

Step 1: Symmetry Check

  • The term x17x^{17} is an odd function because it is raised to an odd power (x17=(x)17x^{17} = -(-x)^{17}).
  • The term cos4(x)\cos^4(x) is an even function because cos(x)\cos(x) is an even function and raising it to any power preserves its evenness.

The product of an odd function (x17x^{17}) and an even function (cos4(x)\cos^4(x)) is odd. An integral of an odd function over a symmetric interval [a,a][-a, a] equals zero:

\int_{-a}^a f(x) \, dx = 0 \quad \text{if f(x) is odd}.

Final Result:

11x17cos4(x)dx=0\int_{-1}^{1} x^{17} \cos^4(x) \, dx = 0

Would you like me to expand on any particular aspect or explore a related problem?

Here are 5 related questions for deeper learning:

  1. Why does the integral of an odd function over a symmetric interval evaluate to zero?
  2. How does the symmetry property apply to even functions in integrals?
  3. What would the result be if the power of xx were even (e.g., x16x^{16})?
  4. How can we evaluate 11cos4(x)dx\int_{-1}^{1} \cos^4(x) \, dx instead?
  5. Can you express cos4(x)\cos^4(x) in terms of trigonometric identities to simplify its integral?

Tip: Always analyze the symmetry of a function before integrating over symmetric intervals—it can save time and simplify computations.

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Math Problem Analysis

Mathematical Concepts

Integration
Odd and Even Functions
Symmetry in Integration

Formulas

\( \int_{-a}^a f(x) \, dx = 0 \) for odd functions over symmetric intervals

Theorems

Odd Function Integral Property

Suitable Grade Level

Grades 11-12 or Undergraduate