4sin(x/2) * cos(x/2) ≤ -1
2sin(x)<=-1
sin(x)<=-1/2
sin(x)=-1/2
x=(-1)^n*arcsin(-1/2)+pi*n
(-1)^n*arcsin(-1/2)+pi*n <=x <= (-1)^(n+1)*arcsin(-1/2)+pi*n>
4sin(x/2)*cos(x/2)<=-1
2sinx<=-1
sinx<=-1/2
sinx=-1/2 x=-П/6+2Пk
x=-5/6П+2Пk
ответ -5/6П+2Пk<=x<=-П/6+2Пk
