precalc
posted by Jess .
Solve:
cos(2x180)  sin(x90)=0
my work:
cos2xcos180 + sin2xsin180= sinxcos90  sin90cosx
cos2x  sin2x= cosx
cos^2x + sin^2x 2sinxcosx=cosx
I'm stuck here. I tried subtracting cosx from both sides and making sin^2x into 1 cos^2x, but I still can't seem to solve the problem.
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