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 - 5.5 Area Of A Surface Of Revolution - Exercises Set 5.5 - Page 380: 5

Answer

$$S = 40\pi \sqrt {82} $$

Work Step by Step

$$\eqalign{ & x = 9y + 1,\,\,\,\,0 \leqslant y \leqslant 2 \cr & {\text{Calculate }}\frac{{dx}}{{dy}} \cr & \frac{{dx}}{{dy}} = 9 \cr & {\text{Use }}S = \int_a^b {2\pi x\sqrt {1 + {{\left( {\frac{{dx}}{{dy}}} \right)}^2}} } dy \cr & S = \int_0^2 {2\pi \left( {9y + 1} \right)\sqrt {1 + {{\left( 9 \right)}^2}} } dy \cr & S = 2\pi \sqrt {82} \int_0^2 {\left( {9y + 1} \right)} dy \cr & {\text{Integrate}} \cr & S = 2\pi \sqrt {82} \left[ {\frac{{9{y^2}}}{2} + y} \right]_0^2 \cr & S = 2\pi \sqrt {82} \left[ {\frac{{9{{\left( 2 \right)}^2}}}{2} + 2} \right] \cr & S = 40\pi \sqrt {82} \cr} $$
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