Решение
а) cos x ≥ √3/2
- arccos(√3/2) + 2πn ≤ x ≤ arccos(√3/2) + 2πn, n∈Z
5π/6 + 2πn ≤ x ≤ π/6 + 2πn, n∈Z
б) tg(x/3 - 1) ≤ -1
- π/2 + πk ≤ (x/3 - 1) ≤ arctg(-1) + πk, k∈z
- π/2 + πk ≤ (x/3 - 1) ≤ - π/4 + πk, k∈z
- π/2 + 1 + πk ≤ (x/3) ≤ - π/4 + 1+ πk, k∈z
- 3π/2 + 3 + 3πk ≤ x ≤ - 3π/4 + 3+ 3πk, k∈z