Решить неравенства 5+cos^2 18x-sin^2 18x ≤ 5

Question

Решить неравенства 5+cos^2 18x-sin^2 18x ≤ 5

Answer 1

Сos²18x-sin²18x≤0
cos36x≤0
π/2+2πn≤36x≤3π/2+2πn,n∈z
x∈[π/72+πn/18;π/24+πn/18,n∈z]