2 cos^2 x=1+2 sin^2 x

Cos^2x - 1/2sin2x + cosx = sinxsin2x = 2sinx*cosxcos^2x - 1/2*2sinx*cosx+cosx = sinxcos^2x - 1/2*2sinx*cosx+cosx - sinx = 0cos^2x-sinx*cosx+cosx-sinx=0cosx (cosx+1) - sinx (cosx+1) = 0 (cosx+1) * (cosx-sinx) = 0 cosx+1=0 - > cosx = - 1 - > x=pi+2pi*K cosx-sinx=0 Делим уравнение на корень из 2sin (pi/4-x) = 0pi/4-x=pi*n x=pi/4-pi*n