sinx/3 ≤ – 1/√2
–(3π/4)+2π·n ≤( x/3) ≤ –(π/4)+2π·n, n ∈ Z Умножаем на 3: –(9π/4)+6π·n ≤ x ≤ –(3π/4)+6π·n, n ∈ Z