Question

Cos x/2= 2 в корне /2

Answer 1

х=пи/4+2*пи*n
и
х=-пи/4+2*пи*n

Answer 2

cos(x/2)=V2/2
x/2=arccos(V2/2)+2π*n  n∈Z
x/2=π/4+2πn  n∈Z
x=π/2+4πn  n∈Z