1) 2cos x= √3;
2) sin x= 1/2;
3) cos 2x= -1

1) 2cox = √3    cosx = √3/2    x = +- arccos(√3/2) + 2πk, k ∈ Z    x = +- π/6 + 2πk2)sin x = 1/2   x = (-1)^k arcsin(1/2) + πk, k ∈ Z   x = (-1)^k π/6 + πk3)cos2x = -1   2x = π + 2πk, k ∈ Z    x = π/2 + πk