Trigonometry 7th Edition

Published by Cengage Learning
ISBN 10: 1111826854
ISBN 13: 978-1-11182-685-7

Chapter 3 - Section 3.2 - Radians and Degrees - 3.2 Problem Set - Page 133: 80


$\frac{-8+3\sqrt 3}{8}$

Work Step by Step

$-1+\frac{3}{4}\cos(2\times\frac{\pi}{6}-\frac{\pi}{2})=-1+\frac{3}{4}\cos(\frac{\pi}{3}-\frac{\pi}{2})$ $=-1+\frac{3}{4}\cos(-\frac{\pi}{6})=-1+\frac{3}{4}\cos\frac{\pi}{6}=-1+\frac{3}{4}\times\frac{\sqrt 3}{2}$ $=-1+\frac{3\sqrt 3}{8}=\frac{-8+3\sqrt 3}{8}$
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