Question

cosxsinπ/8-sinxcosπ/8<0

Answer 1

cos(x)sin(π/8)-sin(x)cos(π/8)<0

sin(π/8-x)<0

Найдём нули

sin(π/8-x)=0<=>π/8-x=πk=>x=π/8+πk

π/8+πk<x<9π/8+πk

k пренадлежит Z