Have you tried the double angle formulas?
Yes. It is just too hard and it would be nice if you would just explain it to me or show me an example. Please.
Hard? Why would anyone want to do something easy?
2cos^2x+cosx=cosx= cos(x)cos(x) - sin(x)sin(x) = cos²(x) - sin²(x)
2 cos^2 x+cosx=cos^2x-(1-cos^2x)
2 cos^2 x+cosx=2cos^2x-1
the only way to make these easy is to do dozens of them, not just the assignments. The double angle formulas are critical to know.
cos 2x + sin x=0
1 - 2sin^2 x + sin x = 0
rearrange things a bit to the usual order:
2sin^2 x - sin x - 1 = 0
(2sin x + 1)(sin x - 1) = 0
so, either sin x = -1/2 or sin x = 1
sin x = -1/2: x = 7pi/6 or 11pi/6
sin x = 1: x = pi/2
Thanks for your help you guys.
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