Multivariable Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 0-53849-787-4
ISBN 13: 978-0-53849-787-9

Chapter 12 - Vectors and the Geometry of Space - 12.2 Exercises - Page 823: 24

Answer

$\langle \frac{-2}{3},\frac{1}{3}, \frac{2}{3}\rangle$

Work Step by Step

Let $\mathbf v=\langle -4,2,4 \rangle$. We can obtain a unit vector in the same direction as $\mathbf v$ by multiplying $\mathbf v$ by $\frac{1}{|\mathbf v|}$. By definition, $|\mathbf v|=\sqrt{(-4)^2+2^2+4^2}=\sqrt{16+4+16}=\sqrt{36}=6$. So $\frac{\mathbf v}{|\mathbf v|}=\frac{\mathbf v}{6}=\frac{\langle -4,2,4 \rangle}{6}=\langle \frac{-4}{6},\frac{2}{6}, \frac{4}{6}\rangle =\langle \frac{-2}{3},\frac{1}{3}, \frac{2}{3}\rangle$ is a unit vector in the same direction as $\mathbf v$.
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