Multivariable Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 0-53849-787-4
ISBN 13: 978-0-53849-787-9

Chapter 16 - Vector Calculus - 16.6 Exercises - Page 1134: 56

Answer

$\approx 4.4506$

Work Step by Step

We have $A(S)= \iint_{D} |\dfrac{\partial r}{\partial u} \times \dfrac{\partial r}{\partial v}|$ 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) $ and $|\dfrac{\partial r}{\partial u} \times \dfrac{\partial r}{\partial v}|=\dfrac{9}{4} |\cos^3 v \sin 2v \sin 2u| \sqrt {\sin^2 v+\dfrac{\cos^2 v \sin^2 2u}{4}}$ Therefore, $A(S)=\iint_{D} \dfrac{9}{4} |\cos^3 v \sin 2v \sin 2u| \sqrt {\sin^2 v+\dfrac{\cos^2 v \sin^2 2u}{4}} dA=\int_0^{\pi} \int_{0}^{2 \pi} \dfrac{9}{4} |\cos^3 v \sin 2v \sin 2u| \sqrt {\sin^2 v+\dfrac{\cos^2 v \sin^2 2u}{4}} dv du$ By using a calculator, we get $A(S) = \int_0^{\pi} \int_{0}^{2 \pi} \dfrac{9}{4} |\cos^3 v \sin 2v \sin 2u| \sqrt {\sin^2 v+\dfrac{\cos^2 v \sin^2 2u}{4}} dv du \approx 4.4506$
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