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: 31



Work Step by Step

$\theta=cos^{-1}\frac{u\cdot v}{|u||v|}=cos^{-1}\frac{(3i+4j)(-2j)}{\sqrt {(3i+4j)(3i+4j)}\sqrt {(-2j)(-2j)}}=cos^{-1}\frac{-8}{\sqrt {9+16}\sqrt 4}=cos^{-1}(-\frac{8}{10})=cos^{-1}(-0.8)$ $\theta=143.13°$
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