Sin^2 (x/2) - cos^2 (x/2) = 0.5

Cos²α-sin²α=cos2α

sin² (x/2) - cos² (x/2) = 0,5

- (cos² (x/2) - sin² (x/2)) = 0,5

-cos (2 * (x/2)) = 0,5

cosx=-0,5

x=-+arccos (-0,5) + 2πn, n∈Z

x = - + (π-arccos0,5) + 2πn, n∈Z

x = - + (π-π/3) + 2πn, n∈Z

x = - + (2/3) * π+2πn, n∈Z