Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 5 - Review Exercises - Page 709: 59

Answer

$\frac{\pi}{6}, \frac{5\pi}{6}, \frac{3\pi}{2}$.

Work Step by Step

Step 1. Rewrite the equation as $2(1-sin^2x)-sin(x)=1$ or $2sin^2(x)+sin(x)-1=0$ Step 2. Let $u=sin(x)$; we have $2u^2+u-1=(2u-1)(u+1)=0$ which gives $u=-1, \frac{1}{2}$ Step 3. For $sin(x)=u=-1$, we have solutions in $[0,2\pi)$ as $x=\frac{3\pi}{2}$ Step 4. For $sin(x)=u=\frac{1}{2}$, we have solutions in $[0,2\pi)$ as $x=\frac{\pi}{6}, \frac{5\pi}{6}$. Step 5. Thus, we have all the solutions in $[0,2\pi)$ as $x=\frac{\pi}{6}, \frac{5\pi}{6}, \frac{3\pi}{2}$.
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