A cosine function has a period of 4, a maximum value of 20, and a minimum value of 0. The function is a not a reflection of its parent function over the x-axis.

Which function could be the function described?

Since the function is not a reflection over the x-axis we know that the maximum of 20 reached is due to a translation up and not an increase in amplitude.

Basic form of a sinusoidal function: F (t) = A Cos (bt - c) + d

|A| = amplitude, distance from max/min to center of the graph.

b = frequency

2π/b = period

c = phase shift, shifts graph left/right

d = vertical shift

Given information:

max = 20; min = 0 so the amplitude is 20/2, A = 10

Center of the graph is then shifted up 10 units. d = 10

period is 4 = 2π/b

b = π/2

* insert the values ...

F (t) = 10 Cos (πt/2) + 10

should look something like that. Maybe has a phase shift, c value or sine instead of cosine would still be a valid solution.