sin^2 x/2=3 cos^2 x/2

sin^2 x/2 = 3(1 - sin^2 x/2).
4sin^2 x/2 = 3.
sin^2 x/2 = 3/4.
1) sin x/2 = -/3 / 2,
x/2 = -pi/3 + 2pi*n.
x = -2pi/3 + 4pi*n.
2) sin x/2 = /3 / 2,
x/2 = pi/3 + 2pi*n.
x = 2pi/3 + 4pi*n.