Question

Помогите пожалуйста решить

Answer 1

f`(x)=[sin²(π/4-x/4)]*sin`(π/4-x/4)*(π/4-x/4)`=2sin(π/4-x/4)*cos(π/4-x/4)*(-1/4)=
=-1/4*sin(π/2-x/2)=-1/4*cos(x/2)
-8*(-1/4*cos(x/2))≥√2
2cos(x/2)≥√2
cos(x/2)≥√2/2
-π/4+2πk≤x/2≤π/4+2πk,k∈z
-π/2+4πk≤x≤π/2+4πk,k∈z