Calculus 8th Edition

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

Chapter 15 - Multiple Integrals - 15.5 Surface Area - 15.5 Exercises - Page 1069: 19

Answer

$$\approx 3.3213$$

Work Step by Step

We write the surface area of the part $z=f(x,y)$ as follows: $A(S)=\iint_{D} \sqrt {1+(f_x)^2+(f_y)^2} dx \ dy$ and, $\iint_{D} dA$ defines the projection of the surface on the xy-plane. Our aim is to calculate the area of the given surface. $$A(S)=\iint_{D} \sqrt{1+(2xy^2)^{2}+(2x^2y)^{2}} \space d A \\ =\iint_{D} \sqrt{1+4x^2y^4+4x^4y^2} \space d A \\=\iint_{D} \sqrt{1+4x^2y^2(x^2+y^2)} \space dA $$ Next, use the polar co-ordinates for of the part $x^2+y^2$ Now, we will use calculator to compute the result as follows: $$A(S)=\int_{0}^{2 \pi} \int_{0}^{1} \sqrt{1+4r^4 \cos^2 \theta \sin^2 \theta \times (r^2)} \times (r) dr d \theta \approx 3.3213$$
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