Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 8 - Polar Coordinates; Vectors - Section 8.6 Vectors in Space - 8.6 Assess Your Understanding - Page 646: 51

Answer

$v \cdot w=0$ We know that when the dot product between the two vectors is $0$, then they are perpendicular or orthogonal. This means that the angle between the two vectors is $90^{\circ}$. Therefore, the angle between the two vectors $v$ and $w$ is $90^{\circ}$.

Work Step by Step

We know that when the dot product between the two vectors is $0$, then they are perpendicular or orthogonal. This means that the angle between the two vectors is $90^{\circ}$. Let us consider two vectors $v=pi+qj+rk$ and $w=xi+yj+zk$. Then we have: $v \cdot w=(pi+qj+rk) \cdot xi+yj+zk =px+qy+rz$ In our case: $v \cdot w=\lt 1,-1, 0 \gt \cdot \lt 1,1,1 \gt= (1)(1) +(-1)(1)+(0)(1) \\=0$ Thus, the two vectors are orthogonal and the angle between them is $90^{\circ}$.
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