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: 45

Answer

\begin{align} \operatorname{curl} \mathbf{F}&= -2e^{x} \cos y \ \ \mathbf{k} \end{align} \begin{align} \operatorname{curl} \mathbf{F}(0,0,1)& = -2\mathbf{k}\\ \end{align}

Work Step by Step

Given $$\mathbf{F}(x, y, z)=e^{x} \sin y \mathbf{i}-e^{x} \cos y \mathbf{j};\ \ \ \ \ (0,0,1) $$ 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} \sin y } \\ {N= -e^{x} \cos y } \\ {P=0}\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} \sin y } & { -e^{x} \cos y } & {0 }\end{array}\right|\\ &=\left(\frac{\partial}{\partial y}( 0)-\frac{\partial}{\partial z}( -e^{x} \cos y )\right) \mathbf{i} -\left(\frac{\partial}{\partial x}(0)-\frac{\partial}{\partial z}(e^{x} \sin y )\right) \mathbf{j} +\left(\frac{\partial}{\partial x}( -e^{x} \cos y )-\frac{\partial}{\partial y}(e^{x} \sin y )\right) \mathbf{k}\\ &=(0-0) \mathbf{i}-(0-0) \mathbf{j}+(-e^{x} \cos y-e^{x} \cos y) \mathbf{k}\\ &=-2e^{x} \cos y \mathbf{k} \end{align} \begin{align} \operatorname{curl} \mathbf{F}(0,0,1)&=-2e^{0} \cos0 \mathbf{k}\\ &=-2 \mathbf{k} \end{align}
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