1) Cosx > -1
- arccos(-1) + 2πn < x < arccos(-1) + 2πn, n∈Z
- π + 2πn < x < π + 2πn, n∈Z<br>2) ctgx < -1<br>arcctg(-1) + πk < x < π + πn, n∈Z<br>3π/4 + πk < x < π + πn, n∈Z<br>3) tgx > -√3
arctg(-√3) + πn < x < π/2 + πn, n∈Z<br>- π/3 + πn < x < π/2 + πn, n∈Z<br>4) cosx < 1/2<br>arccos(1/2) + 2πk < x < 2π - arccos(1/2) + 2πk, k ∈Z
π/3 + 2πk < x < 2π - π/3 + 2πk, k ∈Z
π/3 + 2πk < x < 5π/3 + 2πk, k ∈Z