SOLUTION: 2cos2theta-sintheta=-1

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Question 1157259: 2cos2theta-sintheta=-1
Answer by Boreal(15235) About Me  (Show Source):
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2(1-sin^2 t)-sin t=-1
2-2sin^2 t-sin t=-1
0=2sin^2t+sin^t-3
0=(2 sin t+3)(sin t -1)
sin t=1, and that occurs when theta=90 deg or pi/2 rad.
cos t=0 at pi/2
2 cos^2 pi/2-sin pi/2=0-1=-1