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 8.7 The Cross Product - 8.7 Assess Your Understanding - Page 652: 59

Answer

Please see the proof below.

Work Step by Step

When two vectors $u$ and $v$ are orthogonal, then the angle between these two vectors is given by $90^\circ$. Thus, we have: $||u\times v||=||u||\ ||v||\sin{\theta}\\=||u||\ ||v||\sin{90^\circ}\\=||u||\ ||v|| \ (1)\\=||u|| \ ||v||$ When two vectors $u$ and $v$ are unit vectors, then $||u|| \ ||v|| =1$ Therefore, $||u\times v||=||u||\ ||v||\\=(1)(1)\\=1$ This means that the cross product of two unit vectors is also a unit vector and has magnitude $1$.
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