Sin7xsin9x-sin2xsin4x=0Помогите ребята!

Question

Sin7xsin9x-sin2xsin4x=0
Помогите ребята!

Answer 1

1/2cos2x-1/2cos16x-1/2cos2x+1/2cos6x=0
1/2cos6x-1/2cos16x=0
1/2(cos6x-cos16)=0
1/2*2sin5xsin11x=0
sin5x=0⇒5x=πn⇒x=πn/5,n∈z
sin11x=0⇒11x=πn⇒x=πn/11,n∈z