-4sin(3x/4-pi/4) больше -2√2

Sin(3x/4 - π/4) < √2/2 -5π/4 + 2πk < 3x/4 - π/4 < π/4 + 2πk , k ∈Z -5π/4 + π/4+ 2πk < 3x/4  < π/4 + π/4 + 2πk , k ∈Z -π + 2πk < 3x/4  < π/2 + 2πk , k ∈Z -4π/3 + 8πk/3 < x < 4π/3 + 8πk/3 , k ∈Z