Algebra and Trigonometry 10th Edition

Published by Cengage Learning
ISBN 10: 9781337271172
ISBN 13: 978-1-33727-117-2

Chapter 8 - 8.4 - Vectors and Dot Products - 8.4 Exercises - Page 595: 41



Work Step by Step

$\theta=cos^{-1}\frac{u\cdot v}{|u||v|}=cos^{-1}\frac{(-5i-5j)(-8i+8j)}{\sqrt {(-5i-5j)(-5i-5j)}\sqrt {(-8i+8j)(-8i+8j)}}=cos^{-1}\frac{40-40}{\sqrt {25+25}\sqrt {64+64}}=cos^{-1}~0$ $\theta=90°$
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