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: 25

Answer

$x=\{\frac{2\pi}{3},\frac{4\pi}{3}\}$

Work Step by Step

$2sin(x)+cot(x)-csc(x)=0$ $2sin(x)+\frac{cos(x)}{sin(x)}-\frac{1}{sin(x)}=0\;\;\;\;\;\;\;\;\;\;$ multiply each side by $sin(x)$ $2sin^2(x)+cos(x)-1=0\;\;\;\;\;\;\;\;\;\;\;\;$ $2-2cos^2(x)+cos(x)-1=0$ $2cos^2(x)-cos(x)-1=0$ $cos(x)=\frac{-(-1)\pm \sqrt{(-1)^2-(4.2.(-1))}}{2.2}=1,\frac{-1}{2}$ $cos(x)=1$ $x= cos^{-1}(1)$ $x=0\;\;\;\;\;\;\;\;\;\;\;\;\;\;$ $cos(x)=\frac{-1}{2}$ $x=cos^{-1}(\frac{-1}{2})$ We know $ cos(x) $ is negative in quadrant $II$ and quadrant $III$ $x=\pi +\frac{\pi}{3}\;\;\;\;\;\;\;\;or\;\;\;\;\;\;\;\;x=\pi-\frac{\pi}{3}$ $x=\frac{2\pi}{3}\;\;\;\;\;\;\;\;\;\;\;\;\;\;or\;\;\;\;\;\;\;\;\;\;\;x=\frac{4\pi}{3}$ $x=\{0,\frac{2\pi}{3},\frac{4\pi}{3}\}$
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