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: 11

Answer

$A=11\pi$

Work Step by Step

Given: $r=3+2cos\theta$ First, sketch a graph by plugging in values for $\theta$ (see below), then plug into the polar area formula: $A=0.5\int_a^br^2d\theta=\int_o^\pi(3+2cos\theta)^2d\theta=\int_o^\pi(9+12cos\theta+4cos^2\theta)d\theta$ Since the graph is symmetric, you can just integrate from $0$ to $\pi$ and double the value. Using half angle identities: $A=\int_o^\pi(9+12cos\theta+2+2cos2\theta)\theta)d\theta=(11\theta+12sin\theta+sin2\theta{\vert}_o^\pi)=11\pi$
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