Calculus: Early Transcendentals 8th Edition

Published by Cengage Learning
ISBN 10: 1285741552
ISBN 13: 978-1-28574-155-0

Chapter 10 - Section 10.4 - Areas and Lengths in Polar Coordinates - 10.4 Exercises - Page 672: 4

Answer

$A=\frac{3}{4\pi}$

Work Step by Step

Setting up the integral using the formula for the area of a region in polar coordinates, we get: $$\frac{1}{2}\int_{\pi/2}^{2\pi}\bigg(\frac{1}{\theta}\bigg)^2 d\theta$$ We can rewrite this expression as: $$\frac{1}{2}\int_{\pi/2}^{2\pi}\theta^{-2} d\theta$$ Integrating, we get: $$\frac{1}{2}(-\theta^{-1})\bigg\rvert_{\pi/2}^{2\pi}=\frac{1}{2}\Bigg(-\frac{1}{2\pi}-\bigg(-\frac{1}{\pi/2}\bigg)\Bigg)=\frac{3}{4\pi}$$
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