1)

k∈Z
На промежутке [-2π; π]:
k= -2 x=(π/2) -2π= -3π/2 - да
k= -1 x=(π/2)-π= -π/2 - да
k=0 x=π/2 - да
к=1 x=π/2 + π=3π/2 - нет
2) cosx-1=0
cosx=1
x=2πk, k∈Z
На промежутке [-2π; π]:
k=-1 x= -2π - да
k=0 x=0 - да
k=1 x=2 - нет
Ответ: -2π; -3π/2; -π/2; 0; π/2.