1) 3 tg x/2=√3
tgx/2=√3/3
x/2= π/6+πn
x= π/3+2πn
2) cos 2/3*x = 1/2
2/3*x= ± π/3
2x=±π+6πn
x=±π/2= 3 πn
3) sinx ≥ √3/2
x∈ [ π/3+ 2πn; 2π/3 + 2πn ] n∈ Z
