Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 11 - Three-Dimensional Space; Vectors - 11.4 Cross Product - Exercises Set 11.4 - Page 804: 25

Answer

\[ 16 =V \]

Work Step by Step

If $\vec{w}, \vec{u}$ and $\vec{v}$ are nonzero vectors in 3d-space, then the volume of the shape with $\vec{u}, \vec{v}$ and $\vec{w}$ as contiguous edges is: \[ V=|(\vec{w} \times \vec{v}) \cdot \vec{u}|=a b s\left|\begin{array}{ccc} u_{1} & u_{2} & u_{3} \\ v_{1} & v_{2} & v_{3} \\ w_{1} & w_{2} & w_{3} \end{array}\right| \] It's given that: \[ \vec{w}=\langle 2,2,-4\rangle, \vec{v}=\langle 0,4,-2\rangle \text { and } \vec{u}=\langle 2,-6,2\rangle \] And then \[ \begin{aligned} (\vec{w} \times \vec{v}) \cdot\vec{u} &=\left|\begin{array}{ccc} 2 & -6 & 2 \\ 0 & 4 & -2 \\ 2 & 2 & -4 \end{array}\right| \\ &=-0\left|\begin{array}{cc} -6 & 2 \\ 2 & -4 \end{array}\right|+4\left|\begin{array}{cc} 2 & 2 \\ 2 & -4 \end{array}\right|+2\left|\begin{array}{cc} 2 & -6 \\ 2 & 2 \end{array}\right| \\ &=(12+4)2+(-4-8)4 \\ &-16=32-48 \end{aligned} \] So, the volume is: \[ 16 =|-16|=V \]
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