Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 6 - Trigonometric Functions - 6.2 Trigonometric Functions: Unit Circle Approach - 6.2 Assess Your Understanding - Page 379: 40



Work Step by Step

$5\cos 90^o-8\sin 270^o \\=\left(5\times \cos \dfrac {\pi }{2}\right)-\left(8\times \sin \dfrac {3\pi }{2}\right) \\=(5\times 0)-[8\times \left( -1\right)] \\=0-(-8) \\=8$
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