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Evaluate: ∫-π4π4x3sin4x dx

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Question

Evaluate: `int_(- pi/4)^(pi/4) x^3 sin^4x  "d"x`

Sum
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Solution

Let f(x) = x3.sin4x

∴ f(−x) = (− x)3 [sin (− x)]4 

∴ − x3 (− sin x)4

∴ − f(x)

∴ f(x) is an odd function.

∴ `int_(- pi/4)^(pi/4) x^3 * sin^4x  "d"x` = 0    ......`[∵ int_(-"a")^"a" "f"(x)"d"x` = 0, if f(x) is a odd function.]

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Methods of Evaluation and Properties of Definite Integral
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Chapter 2.4: Definite Integration - Very Short Answers

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