Question

2 sin x•cos 5x-cos 5 x=0

Answer 1

2sinx*cos5x-cos5x=0
cos5x(2sinx-1)=0
cos5x=0                       2sinx-1=0
5x=π/2+πn, n∈Z          sinx=1/2
x=π/10+πn/5, n∈Z       x=(-1)^n*π/6+πk, k∈Z