2sin(x/2+pi/4)< =корень из 2

sin((x/2)–(π/4)) > –1/2

⇒

(–π/6) +2πn < (x/2)–(π/4) < π–(–π/6) + 2πn, n ∈ Z

(–π/6) +2πn < (x/2)–(π/4) < (7π/6) + 2πn, n ∈ Z

(–π/6)+(π/4) +2πn < (x/2) < (7π/6)+ (π/4) + 2πn, n ∈ Z

(π/12) +2πn < (x/2) < (17π/12)+ 2πn, n ∈ Z

(π/6) +4πn < x < (17π/6)+ 4πn, n ∈ Z