Calculate the area of the trapezoid below

The random variable x is the number of occurrences of an event over an interval of ten minutes. it can be assumed that the probability of an occurrence is the same in any two-time periods of an equal length. it is known that the mean number of occurrences in ten minutes is 5.3. the appropriate probability distribution for the random variable

Find the cosine function that is represented in the graph.

What is the frequency of the sinusoidal graph?