Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 14 - Multiple Integrals - 14.2 Double Integrals Over Nonrectangular Regions - Exercises Set 14.2 - Page 1017: 46

Answer

$$2 \pi$$

Work Step by Step

The integration area is a quarter of a circle or a radius of 2. Using the shell method, we get the volume as \[ 2 \pi=\frac{\pi}{2}\left[\frac{x^{4}}{4}\right]_{0}^{2}=\int_{0}^{2} \frac{\pi}{2} x \cdot x^{2} d x \] Using a double integral, \[ \begin{aligned} \iint_{R} f(x, y) d y d z &=\int_{0}^{2} \int_{0}^{\sqrt{4-x^{2}}}\left(y^{2}+x^{2}\right) d y d x \\ &=\int_{0}^{2}\left[x^{2} y+\frac{y^{3}}{3}\right]_{0}^{\sqrt{4-x^{2}}} d x \\ &=\int_{0}^{2} \frac{2}{3} \sqrt{4-x^{2}}\left(x^{2}+2\right) d x \\ &=\left[\frac{2}{3}\left(\frac{1}{4} x\left(x^{2}+2\right) \sqrt{4-x^{2}}+6 \sin ^{-1}\left(\frac{x}{2}\right)\right)\right]_{0}^{2} \\ &=2 \pi \end{aligned} \]
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