Find the general solution for the following equation:
cos 3x+ cos x - cos 2x = 0
cos 3x + cos x - cos 2x = 0
⇒ 2 cos (3x+x2)cos(3x−x2) - cos 2x = 0
⇒ 2 cos 2x cos x - cos 2x =0
⇒ cos 2x (2 cos x-1) = 0
Either cos 2x = 0 or 2 cos x - 1 = 0
⇒ 2x = (2n+1) π2
or cos x = 12 = cos π3, n ϵ Z
⇒ x = (2n+1) π4
or x = 2nπ±π3, n ϵ Z.