2sin^2x-sin2x-4cos^2x=0
sin2x = 2sinx*cosx
2sin^2x-2sinx*cosx-4cos^2x=0
sin^2x-sinx*cosx-2cos^2x=0 Делим на cos^2x
tg^2x-tgx-2=0
D=1+8=9
tgx=2 ->x=arctg 2 +pi*k
tgx=-1 ->x= -pi/4 + pi*l
