Which of the following best corresponds to the x-value where the function f(x)=cos x is a minimum in the interval x = [25,30]?

A) 25.1
B)26.7
C)28.3
D)29.8

Can someone show me how to solve this step by step? Thanks :)

1 answer

you know that cos(x) = -1 at x = π,3π,5π, ...

So, we can check
7π = 21.99
9π = 28.27

Looks like C to me