Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 10 - Parametric Equations and Polar Coordinates - 10.4 Areas and Lengths in Polar Coordinates - 10.4 Exercises - Page 713: 12

Answer

$$\frac{9\pi }{2}$$

Work Step by Step

The area is bounded by $r=2 -\cos \theta$ for $\theta=0$ to $\theta=2\pi$. $$ \begin{aligned} A & =\int_0^{2\pi} \frac{1}{2} r^2 d \theta\\ &=\frac{1}{2} \int_0^{2\pi}(2- \cos \theta)^2 d \theta\\ &= \frac{1}{2} \int_0^{2\pi}(4-4 \cos \theta+\cos^2\theta) d \theta\\ &= \frac{1}{2} \int_0^{2\pi}(\frac{9}{2}-4 \cos \theta+\cos2\theta) d \theta\\ &= \frac{1}{2}\left(\frac{9}{2}\theta-4 \sin \theta+\frac{1}{2}\sin2\theta\right)\bigg|_0^{2\pi}\\ &= \frac{9\pi }{2} \end{aligned} $$
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