1-(cos^2)2x = sin3x - cos(п/2+x)
(cos^2)2x+(sin^2)2x-(cos^2)2x=3sinx-4(sin^3)x+sinx
2(sin^2)2x-4sinx+4(sin^3)x=0
2sinx*cosx-4sinx+4(sin^3)x=0
2sinx(cosx+2(sin^2)x-2)=0
cosx-2+2(sin^2)x=0
cosx-2(sin^2)x-2(cos^2)x+2(sin^2)x=0
cosx-(cos^2)x=0
cosx(1-2cosx)=0
1-2cosx=0
cosx=1/2, значит, x=60градусов