Question

find the general solution of cos 2x =0

Answer 1

cos 2x = 0
cos 90 = 0
and
cos 270 = 0
2x= 2π + π/2
or
2x = 2π - π/2


General Formula:
2x = 2nπ + π/2

or

2x = 2nπ - π/2

x = nπ + π/2

or

x = nπ - π/2

Answer 2

Cos 2 x = 0
Cos 90 = 0  and  cos 270 = 0.
So     2 x =   2π + π/2   or  2π - π/2

General solution:   2 x = 2 n π + π/2   or  2 n π - π/2
    x = n π + π/2   or nπ - π/2