Calculus 8th Edition

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

Chapter 14 - Partial Derivatives - 14.5 The Chain Rule - 14.5 Exercises - Page 984: 24

Answer

$$\dfrac{\partial P}{\partial x} =\dfrac{6}{\sqrt 5} \\ \dfrac{\partial P}{\partial y} =\dfrac{2}{\sqrt 5}$$

Work Step by Step

We have $\dfrac{\partial P}{\partial x} =\dfrac{ue^y}{\sqrt{u^2+v^2+w^2}}+\dfrac{vye^x}{\sqrt{u^2+v^2+w^2}}+\dfrac{wye^{xy}}{\sqrt{u^2+v^2+w^2}}$ For $x=0; y=2$: $\dfrac{\partial P}{\partial x} =\dfrac{0}{\sqrt{(0)^2+(1)^2+(2)^2}}+\dfrac{(2)(2)(e^0)}{\sqrt{(0)^2+(1)^2+(2)^2}}+\dfrac{(1) (2) ( e^0)}{\sqrt{(0)^2+(1)^2+(2)^2}} \\=\dfrac{6}{\sqrt 5}$; Now, $\dfrac{\partial P}{\partial y} =\dfrac{ux(e^y)}{\sqrt{u^2+v^2+w^2}}+\dfrac{v(e^x)}{\sqrt{u^2+v^2+w^2}}+\dfrac{wx(e^{xy})}{\sqrt{u^2+v^2+w^2}}$ For $x=0; y=2$: $\dfrac{\partial P}{\partial y} =\dfrac{0}{\sqrt{(0)^2+(1)^2+(2)^2}}+\dfrac{(2) (e^0)}{\sqrt{(0)^2+(1)^2+(2)^2}}+\dfrac{0}{\sqrt{(0)^2+(1)^2+(2)^2}} \\=\dfrac{2}{\sqrt 5}$
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