Elementary Linear Algebra 7th Edition

Published by Cengage Learning
ISBN 10: 1-13311-087-8
ISBN 13: 978-1-13311-087-3

Chapter 5 - Inner Product Spaces - 5.5 Applications of Inner Product Spaces - 5.5 Exercises - Page 282: 34

Answer

$\frac{(-6,3,-2)}{7}$

Work Step by Step

We know that $ai+bj+ck=(a,b,c).$ We know that for a matrix $ \left[\begin{array}{rrr} a & b & c \\ d &e & f \\ g &h & i \\ \end{array} \right] $ the determinant, $D=a(ei-fh)-b(di-fg)+c(dh-eg).$ A vector orthogonal to $u$ and $v$ is $u\times v$. $u×v$ is the determinant of the matrix $\begin{bmatrix} i& j & k \\ 1& 2&0\\ 1&0 &-3 \\ \end{bmatrix} $ Thus $u×v=(-6,3,-2).$ And a unit vector parallel to this is: $\frac{u\times v}{|u\times v|}=\frac{(-6,3,-2)}{\sqrt{(-6)^2+3^2+(-2)^2}}=\frac{(-6,3,-2)}{\sqrt{49}}=\frac{(-6,3,-2)}{7}$
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