Not sure if this is right forum, but hopefully is.

The height, h centimeters, of a bicycle pedal above the ground at time t seconds is given by the equation:Calculate the maximum and minimum heights of the pedal

h=30+15cos90t°

(a)

(b)Find the first two positive values of t for which the height of the pedal is 43 cm.

(c)How many revolutions does the pedal make in one minute?

To calculate the max and min, the differential would equal 0 and to determine

if the point is a max or a min, the second differential would be positive or neg?

I know that the differential of cos is -sin, but how do I differentiate something like this?

Also, how do I go about 'c' for that matter?