Answer:
A = 0 +/- nπ radians , where n is an integer.
Step-by-step explanation:
cos 2A = cos^2 A
Use the identity cos 2A = 2 cos^2 A -1 :
2cos^2 A - 1 = cos^2 A
cos^2 A = 1
Cos A = +/-1
When cos A = 1, A = 0 +/- 2nπ radians.
when cos A = -1, A = π +/- nπ radians.
