Hello. I am stuck at a point on this question.

Identify the maximum and minimum values of the function y = 10 cos x in the interval [-2π, 2π].

This is what I have so far (not much I know)

10 cos [-2π]=10

10 cos [2π]=10

f(x)=10 sin (x)

0=10 sin (x)

0=sin (x)

Nothing like the examples I was given in class so now I can't figure out what to do. Is anyone able to explain this to me please?

Thanks everybody.