Precalculus (6th Edition) Blitzer

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

Chapter 4 - Test - Page 647: 18


$ -\sqrt 3$

Work Step by Step

Step 1. Let $u=cos^{-1}(-\frac{1}{2})$; we have $cos(u)=-\frac{1}{2}$ Step 2. As $u\in[0,\pi]$, we know $u$ is in quadrant II and $sin(u)\gt0$ Step 3. We have $sin(u)=\sqrt {1-cos^2(u)}=\sqrt {1-\frac{1}{4}}=\frac{\sqrt 3}{2}$ Step 4. Combining the above results, we have $tan(u)=\frac{sin(u)}{cos(u)}=-\sqrt 3$ Step 5. Thus we have $tan(cos^{-1}(-\frac{1}{2}))= -\sqrt 3$
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