1)найти все корни уравнения принадлежащие отрезку от [0; 3п] sin2x=-1/2 2) найти все решения неравенства принадл. отрезку [0; 3п] cosx> =1/2 и sin2x> =-1/2

1
sin2x=-1/2
2x=-π/6+2πk U 2x=-5π/6+2πk
x=-π/12+πk U x=-5π/12+πk,k∈z
0≤-π/12+πk≤3π
0≤-1+12k≤36
1/12≤k≤37/12
k=1  x=-π/12+π=11π/12
k=2  x=-π/12+2π=23π/12
k=3  x=-π/12+3π=35π/12
x=-π/12+πk U x=-5π/12+πk,k∈z
0≤-5π/12+πk≤3π
0≤-5+12k≤36
5/12≤k≤41/12
k=1  x=-5π/12+π=7π/12
k=2  x=-5π/12+2π=19π/12
k=3  x=-5π/12+3π=31π/12
2
cosx≥1/2
x∈[-π/3+2πk;π/3+2πk,k∈z]

sin2x≥-1/2
-π/6+2πk≤2x≤7π/6+2πk
x∈[-π/12+πk;7π/12+πk,k∈z]