cos(3π/2 - 0.5x)=0.5

cos(3π/2 - 0.5x) = 0.5
-cos 0.5x = 0.5
cos 0.5x = -0.5
1) 0.5x = 2π/3 + 2πk → x1 = 4π/3 + 4πk
2) 0.5x = -2π/3 + 2πk → x2 = -4π/3 + 4πk
Ответ: х = +- 4π/3 + 4πk  (k∈Z)