РЕШЕНИЕ
cos( x/2 + 1/4 ) ≤ - √2 /2arccos (- √2/2) + 2πn ≤ x/2 + 1/4 ≤ 2π - arccos(-√2/2) + 2πn, n ∈ Z3π/4 + 2πn ≤ x/2 + 1/4 ≤ 2π - 3π/4 + 2πn, n ∈ Z3π/4 + 2πn ≤ x/2 + 1/4 ≤ 5π/4 + 2πn, n ∈ Z3π/4 - 1/4 + 2πn ≤ x/2 ≤ 5π/4 - 1/4 + 2πn, n ∈ Z3π/2 - 1/2 + 4πn ≤ x ≤ 5π/2 - 1/2 + 4πn, n ∈ Z