Definite Integration Question 483

Question: $ \int_0^{\pi }{x\sin xdx=} $

[SCRA 1980, 91]

Options:

A) $ \pi $

B) 0

C) 1

D) $ {{\pi }^{2}} $

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Answer:

Correct Answer: A

Solution:

$ I=\int_0^{\pi }{x\sin xdx=\int_0^{\pi }{(\pi -x)\sin xdx}} $

therefore $ 2I=\pi \int_0^{\pi }{\sin xdx=\pi [-\cos x]_0^{\pi }\Rightarrow I=\pi } $ .