Calculus 10th Edition

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

Chapter 11 - Vectors and the Geometry of Space - Review Exercises - Page 811: 37

Answer

\[\frac{8}{\sqrt{377}}\mathbf{i}+\frac{12}{\sqrt{377}}\mathbf{j}+\frac{13}{\sqrt{377}}\mathbf{k}\]

Work Step by Step

\[\begin{align} & \text{Let }\mathbf{u}=\left\langle 2,-10,8 \right\rangle \text{ and }\mathbf{v}=\left\langle 4,6,-8 \right\rangle \\ & \text{Find }\mathbf{u}\times \mathbf{v} \\ & \mathbf{u}\times \mathbf{v}=\left| \begin{matrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \\ 2 & -10 & 8 \\ 4 & 6 & -8 \\ \end{matrix} \right| \\ & \mathbf{u}\times \mathbf{v}=\left| \begin{matrix} -10 & 8 \\ 6 & -8 \\ \end{matrix} \right|\mathbf{i}-\left| \begin{matrix} 2 & 8 \\ 4 & -8 \\ \end{matrix} \right|\mathbf{j}+\left| \begin{matrix} 2 & -10 \\ 4 & 6 \\ \end{matrix} \right|\mathbf{k} \\ & \mathbf{u}\times \mathbf{v}=32\mathbf{i}+48\mathbf{j}+52\mathbf{k} \\ & \\ & \text{Finding a unit vector that is orthogonal to both }\mathbf{u}\text{ and }\mathbf{v} \\ & \frac{\mathbf{u}\times \mathbf{v}}{\left\| \mathbf{u}\times \mathbf{v} \right\|}=\frac{32\mathbf{i}+48\mathbf{j}+52\mathbf{k}}{\sqrt{{{\left( 32 \right)}^{2}}+{{\left( 48 \right)}^{2}}+{{\left( 52 \right)}^{2}}}} \\ & \frac{\mathbf{u}\times \mathbf{v}}{\left\| \mathbf{u}\times \mathbf{v} \right\|}=\frac{1}{\sqrt{6032}}\left( 32\mathbf{i}+48\mathbf{j}+52\mathbf{k} \right) \\ & \frac{\mathbf{u}\times \mathbf{v}}{\left\| \mathbf{u}\times \mathbf{v} \right\|}=\frac{1}{4\sqrt{377}}\left( 32\mathbf{i}+48\mathbf{j}+52\mathbf{k} \right) \\ & \frac{\mathbf{u}\times \mathbf{v}}{\left\| \mathbf{u}\times \mathbf{v} \right\|}=\frac{32}{4\sqrt{377}}\mathbf{i}+\frac{48}{4\sqrt{377}}\mathbf{j}+\frac{52}{4\sqrt{377}}\mathbf{k} \\ & \frac{\mathbf{u}\times \mathbf{v}}{\left\| \mathbf{u}\times \mathbf{v} \right\|}=\frac{8}{\sqrt{377}}\mathbf{i}+\frac{12}{\sqrt{377}}\mathbf{j}+\frac{13}{\sqrt{377}}\mathbf{k} \\ \end{align}\]
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