Calculus, 10th Edition (Anton)

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

Chapter 5 - Applications Of The Definite Integral In Geometry, Science, And Engineering - 5.3 Volumes By Cylindrical Shells - Exercises Set 5.3 - Page 370: 23

Answer

(a) $V=\frac{7 \pi}{30}$ (b) Easier

Work Step by Step

Write formule for the volume using cylindrical shells (a) $\int_{0}^{1} 2 \pi x\left(x^{3}-3 x^{2}+2 x\right) d x=V$ Determine antiderivative $$ \begin{array}{c} \left.2 \pi\left(\frac{x^{5}}{5}-\frac{3 x^{4}}{4}+\frac{2 x^{3}}{3}\right)\right|_{0} ^{1}=V \\ \frac{7 \pi}{30}=V \end{array} $$ (b) The method of using cylindrical shells would be much simpler than the method of cutting, since in order for us to use the method of cutting, we need to decide the inverse function of the shell. $x^{3}-3 x^{2}+2 x=y$ (or rewrite this equation as $f(y))=x$ which will be very difficult to determine.
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