sin(x + (π/4)) ≤ √2/2
Пусть x + (π/4) = a, тогда sin(a) ≤ √2/2 ⇒
(3π/4) + 2πn ≤ a ≤ (9π/4) + 2πn
(3π/4) + 2πn ≤ x + (π/4) ≤ (9π/4) + 2πn
Отнимем от каждой части неравенства π/4
(π/2) + 2πn ≤ x ≤ 2π + 2πn, n ∈ Z
ОТВЕТ: [ (π/2) + 2πn ; 2π + 2πn ] , n ∈ Z