Answer
$8$
Work Step by Step
$5\cos 90^o-8\sin 270^o
\\=\left(5\times \cos \dfrac {\pi }{2}\right)-\left(8\times \sin \dfrac {3\pi }{2}\right)
\\=(5\times 0)-[8\times \left( -1\right)]
\\=0-(-8)
\\=8$
Precalculus (10th Edition)
by Sullivan, Michael
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
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