А
2π/3+2πn<3x<4π/3+2πn<br>2π/9+2πn/3x∈(2π/9+2πn/3;4π/9+2πn,n∈z)
б
sinx>1/2
π/6+2πn<2x<5π/6+2πn<br>π/12+πnx∈(π/12+πn;5π/12+πn,n∈z)
в
-tgx/2<1<br>tgx/2>-1
-π/4+πn-π/2+2πnx∈(-π/2+2πn;π+2πn,n∈z)
(это верный ответ,а то отметите ошибку)
г
sin2x≥√2/2
π/4+2πn≤2x≤3π/4+2πn
π/8+πn≤x≤3π/8+πn,n∈z
x∈[π/8+πn;3π/8+πn,n∈z]