Answer: 40 sec
Explanation:
Given : The height, h, in feet of a piece of cloth tied to a waterwheel in relation to sea level as a function of time, t, in seconds can be modeled by the equation.

The general form of cosine function is
, where period of the function is represented by
.
As we compare the given cosine function yo the general cosine function , we get

Then , the period of the function will be :-

Hence, it takes 40 seconds for the waterwheel to complete one turn.