University Calculus: Early Transcendentals (3rd Edition)

Published by Pearson
ISBN 10: 0321999584
ISBN 13: 978-0-32199-958-0

Chapter 15 - Practice Exercises - Page 909: 10

Answer

$0$

Work Step by Step

The parametric equations are: $ x=2 \cos t , y=2 \sin t$ Here, we have $ dx= -2 \sin t dt, dy=2 \cos t dt$ Plug the above values in the given integral. $\int_{0}^{2 \pi}( -2 \sin t )^2 (-2 \sin t dt)+(2 \cos t)^2 (2 \cos t dt)= \int_{0}^{2 \pi} (-8\sin^2 t+8 \cos^3 t) dt$ $\int_{0}^{2 \pi} (-8\sin t(1-\cos^2 t)+8 \cos t(1-\sin^2 t) ) dt=\int_{0}^{2 \pi} -8 sin t +8 \sin t\cos^2 t +8 \cos t -8 \cos t \sin^2 t$ Thus, we have $[8\cos t-\dfrac{8}{3}\cos^3 t+8 \sin t-\dfrac{8}{3}\sin^3 t]_{0}^{2 \pi} =(8\cos (2 \pi)-\dfrac{8}{3}\cos^3 (2 \pi)+8 \sin (2 \pi)-\dfrac{8}{3}\sin^3 (2 \pi))-(8\cos (0)-\dfrac{8}{3}\cos^3 (0)+8 \sin (0)-\dfrac{8}{3}\sin^3 (0))= 0$
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