Question

$0,5sin4x textless -0,2$

Answer 1

sin4x<-0,4
π+arcsin0,4+2πn<4x<2π-arcsin0,4+2πn
π/4+1/4*arcsin0,4+πn/2<x<π/2-1/4*arcsin0,4+πn/2,n∈z