Please Help me with this...

Find the values of x for which the equation cos x = –1 is true. Let k represent an integer..
These are the answer choices ::
2(pi)k
(pi)/2 + 2k
(pi) + 2(pi)k
3(pi)/2+ 2(pi)k

Well when is cosx = -1 the first time?

At π... 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

cos(x)=-1 happens at (pi), 3(pi), 5(pi), ...

the pattern of the constant is 1, 3, 5, 7, 9, 11..
we can express the pattern as (2k+1)(pi) or simply (pi) + 2(pi)k.

for cos x = -1 ==> x = 2(pi)

1. 2(pi)k = 180deg = 2(pi) rad ==> k =1
2. (pi)/2 + 2k = 2(pi) ==> 2k = 1.5(pi) ==> k = 0.75(pi)
3. (pi) + 2(pi)k = 2(pi) ==> 1+2k = 2 (divided by pi) ==> 2k =1 ==> k= 1/2
4. 3(pi)/2+ 2(pi)k = 2(pi) ==> (3/2) + 2k = 2 ==> 2k = 2-1.5 = 0.5 ==> k = 0.25