Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 16 - Vector Calculus - 16.6 Parametric Surfaces and Their Areas - 16.6 Exercises - Page 1162: 56

Answer

$\approx 4.4506$

Work Step by Step

$Surafce \ area ; A(S)= \iint_{D} |\dfrac{\partial r}{\partial u} \times \dfrac{\partial r}{\partial v}| \ dA$ and $\iint_{D} dA$ is the area of the region $D$ Now, $\dfrac{\partial r}{\partial u} \times \dfrac{\partial r}{\partial v}=\dfrac{9}{4} \cos^3 v \sin 2v \sin 2u (sin u \sin vi+\cos u \sin v j+\cos v \cos u \sin u k) $ Therefore, $Surface \ area ; A(S)=\iint_{D} \dfrac{9}{4} |\cos^3 v \sin 2v \sin 2u| \sqrt {\sin^2 v+\dfrac{\cos^2 v \sin^2 2u}{4}} \ dA \\ =\iint_{D} \dfrac{9}{4} |\cos^3 v \sin 2v \sin 2u| \sqrt {\sin^2 v+\dfrac{\cos^2 v \sin^2 2u}{4}} dA \\ =\int_0^{\pi} \int_{0}^{2 \pi} \dfrac{9}{4} |\cos^3 v \sin 2v \sin 2u| \sqrt {\sin^2 v+\dfrac{\cos^2 v \sin^2 2u}{4}} dv du$ Now, we will use calculator to get as follows: $Surface \ Area; A(S) = \int_0^{\pi} \int_{0}^{2 \pi} \dfrac{9}{4} |\cos^3 v \sin 2v \sin 2u| \sqrt {\sin^2 v+\dfrac{\cos^2 v \sin^2 2u}{4}} \ dv \ du \approx 4.4506$
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