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|

Answer: On the interval [25, 30] the function y = cos x is at it's minimum at x = 9pi or about 28.26.

The graph of y = cos x starts at 1 and moves in the shape of a wave from - 1 to 1. It reaches it's first minimum value when x = pi. The period of the wave is 2 pi.

Therefore, it is at its lowest value at the following values, 1pi, 3pi, 5pi, 7pi, 9pi ... The value in our given interval is 9pi.