Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 7 - Principles Of Integral Evaluation - 7.2 Integration By Parts - Exercises Set 7.2 - Page 499: 56

Answer

$$A = \frac{{{\pi ^2}}}{8} - 1$$

Work Step by Step

$$\eqalign{ & x \geqslant x\sin x{\text{ on the interval }}\left[ {0,\frac{\pi }{2}} \right],{\text{ then}} \cr & {\text{The area is given by}} \cr & A = \int_0^{\pi /2} {\left( {x - x\sin x} \right)dx} \cr & {\text{Integrating}} \cr & A = \int_0^{\pi /2} {xdx} - \underbrace {\int_0^{\pi /2} {x\sin xdx} }_{\operatorname{int} {\text{ by parts}}} \cr & A = \left[ {\frac{{{x^2}}}{2}} \right]_0^{\pi /2} - \left[ {\sin x - x\cos x} \right]_0^{\pi /2} \cr & A = \left[ {\frac{{{x^2}}}{2} + x\cos x - \sin x} \right]_0^{\pi /2} \cr & {\text{Evaluate}} \cr & A = \left[ {\frac{{{{\left( {\pi /2} \right)}^2}}}{2} + \frac{\pi }{2}\cos \left( {\frac{\pi }{2}} \right) - \sin \left( {\frac{\pi }{2}} \right)} \right] - \left[ 0 \right] \cr & A = \frac{{{\pi ^2}}}{8} - 1 \cr} $$
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