cos^2x-sin^2x>-sqrt(3)/2
Формула: cos^2x-sin^2x=cos2x сos2x > - sqrt(3)/2 -(2π/3)+2πn < 2x < (2π/3)+2πn, n ∈ Z Делим на 2 [b]-(π/3)+πn < x < (π/3)+πn, n ∈ Z[/b]