Calculus: Early Transcendentals (2nd Edition)

Published by Pearson
ISBN 10: 0321947347
ISBN 13: 978-0-32194-734-5

Chapter 11 - Vectors and Vector-Valued Functions - 11.4 Cross Products - 11.4 Exercises - Page 797: 33

Answer

\[\begin{align} & \mathbf{u}\times \mathbf{v}=8\mathbf{i}+4\mathbf{j}+10\mathbf{k} \\ & \mathbf{v}\times \mathbf{u}=-8\mathbf{i}-4\mathbf{j}-10\mathbf{k} \\ \end{align}\]

Work Step by Step

\[\begin{align} & \mathbf{u}=3\mathbf{i}-\mathbf{j}-2\mathbf{k},\text{ }\mathbf{v}=\mathbf{i}+3\mathbf{j}-2\mathbf{k} \\ & \text{Calculate the cross product }\mathbf{u}\times \mathbf{v} \\ & \mathbf{u}\times \mathbf{v}=\left| \begin{matrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \\ 3 & -1 & -2 \\ 1 & 3 & -2 \\ \end{matrix} \right| \\ & \mathbf{u}\times \mathbf{v}=\left| \begin{matrix} -1 & -2 \\ 3 & -2 \\ \end{matrix} \right|\mathbf{i}-\left| \begin{matrix} 3 & -2 \\ 1 & -2 \\ \end{matrix} \right|\mathbf{j}+\left| \begin{matrix} 3 & -1 \\ 1 & 3 \\ \end{matrix} \right|\mathbf{k} \\ & \mathbf{u}\times \mathbf{v}=\left( 2+6 \right)\mathbf{i}-\left( -6+2 \right)\mathbf{j}+\left( 9+1 \right)\mathbf{k} \\ & \mathbf{u}\times \mathbf{v}=8\mathbf{i}+4\mathbf{j}+10\mathbf{k} \\ & \text{Calculate the cross product }\mathbf{v}\times \mathbf{u} \\ & \mathbf{v}\times \mathbf{u}=\left| \begin{matrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \\ 1 & 3 & -2 \\ 3 & -1 & -2 \\ \end{matrix} \right| \\ & \mathbf{v}\times \mathbf{u}=\left| \begin{matrix} 3 & -2 \\ -1 & -2 \\ \end{matrix} \right|\mathbf{i}-\left| \begin{matrix} 1 & -2 \\ 3 & -2 \\ \end{matrix} \right|\mathbf{j}+\left| \begin{matrix} 1 & 3 \\ 3 & -1 \\ \end{matrix} \right|\mathbf{k} \\ & \mathbf{v}\times \mathbf{u}=\left( -6-2 \right)\mathbf{i}-\left( -2+6 \right)\mathbf{j}+\left( -1-9 \right)\mathbf{k} \\ & \mathbf{v}\times \mathbf{u}=-8\mathbf{i}-4\mathbf{j}-10\mathbf{k} \\ \end{align}\]
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