Trigonometry 7th Edition

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

Chapter 6 - Section 6.2 - More on Trigonometric Equations - 6.2 Problem Set - Page 332: 18



Work Step by Step

$cos(2x)-cos(x)-2=0$ $2cos^2(x)-1-cos(x)-2=0\;\;\;\;\;\;\;\;\;\;$ $2cos^2(x)-cos(x)-3=0\;\;\;\;\;\;\;\;\;\;\;\;$ $cos(x)=\frac{-(-1)\pm \sqrt{(-1)^2-(4.2.(-3))}}{2.2}=-1,\frac{3}{2}$ $cos(x)=-1$ $\theta= cos^{-1}(-1)$ $x=\pi\;\;\;\;\;\;\;\;\;\;\;\;\;\;$ $cos(\theta)=\frac{3}{2}$ $x=$No solution because cosine line between 1 and -1 $x=\{\pi\}$
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