Answer
$-\frac{3}{5}$
Work Step by Step
The identity says: $sin^2(\theta)+cos^2(\theta)=1$. Hence $cos(\theta)=\pm\frac{3}{5}$, but it is in quadrant II, hence $cos(\theta)=-\frac{3}{5}$
Precalculus (10th Edition)
by Sullivan, Michael
Published by
Pearson
ISBN 10:
0-32197-907-9
ISBN 13:
978-0-32197-907-0
Chapter 7 - Analytic Trigonometry - 7.5 Sum and Difference Formulas - 7.5 Assess Your Understanding - Page 487: 2
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