Calculus 10th Edition

Published by Brooks Cole
ISBN 10: 1-28505-709-0
ISBN 13: 978-1-28505-709-5

Chapter 15 - Vector Analysis - 15.1 Exercises - Page 1049: 46

Answer

\begin{align} \operatorname{curl} \mathbf{F}&=-x(z-y) e^{-x y z}\mathbf{i} +y(z-x) e^{-x y z}\mathbf{j} -z(y -x) e^{-x y z}\mathbf{k} \end{align} \begin{align} \operatorname{curl} \mathbf{F}(3,2,0)& =6 \mathbf{i}-6 \mathbf{j} \\ \end{align}

Work Step by Step

Given $$\mathbf{F}(x, y, z)=e^{-x y z}(\mathbf{i}+ \mathbf{j}+ \mathbf{k})\\ =e^{-x y z} \mathbf{i}+e^{-x y z} \mathbf{j}+e^{-x y z} \mathbf{k} ;\ \ \ \ \ (3,2,0) $$ Since \begin{align}\mathbf{F}(x,y)&=M \mathbf{i}+N\mathbf{j}+P\mathbf{k}\end{align} we get \begin{array}{l} {M=e^{-x y z}} \\ {N=e^{-x y z}} \\ {P=e^{-x y z}}\end{array} therefore we have \begin{align} \operatorname{curl} \mathbf{F}&=\left|\begin{array}{ccc}{\mathbf{i}} & {\mathbf{j}} & {\mathbf{k}} \\ {\frac{\partial}{\partial x}} & {\frac{\partial}{\partial y}} & {\frac{\partial}{\partial z}} \\ {M} & {N} & {P}\end{array}\right|\\ &=\left|\begin{array}{ccc}{\mathbf{i}} & {\mathbf{j}} & {\mathbf{k}} \\ {\frac{\partial}{\partial x}} & {\frac{\partial}{\partial y}} & {\frac{\partial}{\partial z}} \\ {e^{-x y z}} & {e^{-x y z}} & {e^{-x y z}}\end{array}\right|\\ &=\left(\frac{\partial}{\partial y}(e^{-x y z})-\frac{\partial}{\partial z}(xe^{-x y z})\right) \mathbf{i}\\ & \quad-\left(\frac{\partial}{\partial x}(e^{-x y z})-\frac{\partial}{\partial z}(e^{-x y z})\right) \mathbf{j}\\ & \quad+\left(\frac{\partial}{\partial x}(e^{-x y z})-\frac{\partial}{\partial y}(e^{-x y z})\right) \mathbf{k}\\ &=(-xze^{-x y z}-(-xy)e^{-x y z}) \mathbf{i}\\ &\quad-(-yze^{-x y z}-(-xy)e^{-x y z}) \mathbf{j}\\ &\quad+(-yze^{-x y z}-(-xz)e^{-x y z}) \mathbf{k}\\ &=(-xz+xy) e^{-x y z}\mathbf{i} -(-yz+xy) e^{-x y z}\mathbf{j} +(-yz +xz) e^{-x y z}\mathbf{k}\\ &=-x(z-y) e^{-x y z}\mathbf{i} +y(z-x) e^{-x y z}\mathbf{j} -z(y -x) e^{-x y z}\mathbf{k} \end{align} \begin{align} \operatorname{curl} \mathbf{F}(3,2,0) &=-x(z-y) e^{-x y z}\mathbf{i} +y(z-x) e^{-x y z}\mathbf{j} -z(y -x) e^{-x y z}\mathbf{k} &=4 \mathbf{i}- \mathbf{j}-3\mathbf{k}\\ &=-3(0-2) e^{0}\mathbf{i} +2(0-3) e^{0}\mathbf{j} -0(2 -3) e^{0}\mathbf{k} \\ &=6 \mathbf{i} -6 \mathbf{j} \end{align}
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