sin^2 x=1-cos^2 x 6*(1-cos^2 x) - 5cosx + 5=0 6-6cos^2 x - 5cos x + 5=0 -6cos^2x-5cos x + 11=0 6cos^2 x + 5 cos x -11=0 cos x=y 6y^2+5y-11=0 D= 289 y1=(-5+17)/12=1 y2= (-5-17)/12=-11/6 - не подходит, т.к. -1<=сos x<=1 cos x=1 x=0
