Multivariable Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 0-53849-787-4
ISBN 13: 978-0-53849-787-9

Chapter 15 - Multiple Integrals - 15.4 Exercises - Page 1026: 29

Answer

$\int_{-3}^3\int_0^{\sqrt{9-x^2}}\sin (x^2+y^2)dydx=\frac{\pi}{2}-\frac{\pi\cos 9}{2}$

Work Step by Step

The set of points $R=\{(x,y)|-3\leq x\leq 3,\leq y\leq \sqrt{9-x^2}\}$ describes the region of an upper semicircle center at the origin with the radius of $3$. Then, in polar coordinates $R=\{(r,\theta)|0\leq r\leq 3,0\leq\theta \leq\pi\}$. Convert the integral to polar coordinates and evaluate: $\int_{-3}^3\int_0^{\sqrt{9-x^2}}\sin(x^2+y^2)dydx=\int_0^3\int_0^\pi \sin(r^2)\cdot rd\theta dr$ $=\int_0^3\theta r\sin(r^2)]_0^{\pi}dr$ $=\int_0^3\pi r\sin(r^2)dr$ $=-\frac{\pi\cos(r^2)}{2}]_{0}^3$ $=\frac{\pi}{2}-\frac{\pi\cos 9}{2}$
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