2sinx cosx+ 3 cos^2 x- sin ^2x = 0

sin2x+3cosк^2х-sin^2x=0
sin2x+3(1-sin^2x)-sin^2x=0
sin2x+3-3sin^2x-sin^2x=0
sin2x+3-4sin^2x=0
sin2x+3-4sin^2x=0
4sin^2x-sin2x-3=0
sin2x=a
4a^2-a-3=0
D=49
a1=1;  a2=-3/4
sin2x=1
2x=п/2+  2пк
х=п/4+пк