Cos 5x + cos 7x - cos 6x=0

Question

Cos 5x + cos 7x - cos 6x=0

Answer 1

2cos6xcosx-cos6x=0
cos6x(2cosx-1)=0
cos6x=0⇒6x=π/2+πn⇒x=π/12+πn/6
cosx=1/2⇒x=+-π/3+2πn