2sin^2 0.5x-cos^2x=1​

1 - cos(x) - cos(x)^2 = 1

cos(x)^2 + cos(x) = 0

cos(x)(cos(x) + 1) = 0

cos(x) = 0 cos(x)=-1

x = π/2 + πn x = π +2πk