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 498: 36

Answer

$\frac{\pi^{2}}{2}$-2

Work Step by Step

Step 1: Split the integral $\int$(x+xcosx)dx=$\int$xdx+$\int$xcosxdx=$\frac{x^{2}}{2}$+$\int$xcosxdx Step 2: We evaluate $\int$xcosxdx with integration by parts. Let u=x and dv=cosxdx, so v=$\int$cosxdx=sinx. $\int$xcosxdx=xsinx-$\int$sinxdx And $\int$sinxdx=-cosx So, the expression=xsinx-(-cosx)+C=xsinx+cosx+C Step 3: Finally substitute $\int$xcosxdx in step 1 with (xsinx+cosx+C): $\int$(x+xcosx)dx=$\frac{x^{2}}{2}$+xsinx+cosx+C And $\int^{\pi}_{0}$(x+xcosx)dx=$\frac{\pi^{2}}{2}$+$\pi$sin$\pi$+cos$\pi$-($\frac{0^{2}}{2}$+0sin0+cos0)=$\frac{\pi^{2}}{2}$-2
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