sin(2x)-sin(x)=0

2sin(x)cos(x)-sin(x)=0

sin(x)(2cos(x)-1)=0

1)  sin(x)=o

x=pi*n

2) 2cos(x)-1=0

cos(x)=1/2

x=+-arccos(1/2)+2*pi*n

x=+-pi/3+2*pi*n