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Multiple Choice
Evaluate the integral. (Use c for the constant of integration.)
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Verified step by step guidance
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Step 1: Recognize that the integral involves trigonometric functions raised to powers. To simplify, use trigonometric identities or substitution methods. Specifically, consider using the identity \( \sin^2(x) = 1 - \cos^2(x) \) to rewrite \( \sin^2(x) \) in terms of \( \cos(x) \).
Step 2: Rewrite the integral \( \int 9 \sin^2(x) \cos^3(x) \, dx \) as \( \int 9 (1 - \cos^2(x)) \cos^3(x) \, dx \). This simplifies the expression and prepares it for integration.
Step 3: Expand the integrand to separate terms: \( \int 9 \cos^3(x) \, dx - \int 9 \cos^5(x) \, dx \). Now, you have two simpler integrals to evaluate.
Step 4: Use substitution for each term. Let \( u = \cos(x) \), then \( du = -\sin(x) \, dx \). Substitute into the integral, transforming it into a polynomial in \( u \). For example, \( \int \cos^3(x) \, dx \) becomes \( \int u^3 (-du) \).
Step 5: Integrate each term in \( u \)-form. For \( \int u^3 (-du) \), the result is \( -\frac{u^4}{4} \). Similarly, integrate \( \int u^5 (-du) \) to get \( -\frac{u^6}{6} \). Substitute back \( u = \cos(x) \) and combine terms to express the final result in terms of \( \sin(x) \) and \( \cos(x) \). Add the constant of integration \( c \).