Question

thanks

Answer 1

Well when is cosx = -1 the first time in the circle?

At π (because x=180 degrees)... right?

So now when does it occur again, well it doesnt happen again until we go around in a full circle.
So another 2π and this will happen indefinitely for any integer k.

So the answer is:
π + 2πk

Answer 2

cos x=-1
x = cos^-1 (-1) = 180* for [0,360] cycle
x = 180* + 360k where k represents an integer.

Answer 3

I would say C