Where is cosx equal to -1

Where is cosx= -1 ? from (-infinity, +infinity) using n
I know cosx is equal to -1 at (pi) when the interval is (0, 2(pi)] but what about at all pi?

Cosinus has a cycle of 2(pi), so that means it'll be -1 at (pi) + 2k(pi), k is an integer from zero upwards.