0.5(sin3.5x-sin1.5x)-0.5(sin3.5x-sin(x/2))=0

0.5(sin3.5x-sin1.5x-sin3.5x+sin(x/2))=0

-0.5(sin1.5x-sin(x/2))=0

sin1.5x-sin(x/2)=0

2sin(x/2)*cosx=0

sin(x/2)=0;x1=pik;

cosx=0; x2=pi/2+pik; k∈Z