SOLUTION: Cos(2x)+cosx=0

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Question 1075523: Cos(2x)+cosx=0
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
2 cos^2 x-1=cos 2x
2 cos^2x-1+cos x=0
rewrite as 2 cos^2 x+cos x-1=0
(2 cos x-1)(cos x+1)=0
cos x=1/2
cos x=-1
This works at pi, pi/3 and 5pi/3
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