Find the cosine function that is represented in the graph.

f(x)=4cos(5x)

Step-by-step explanation:

Let us see the standard form of cosine function

f(x) = acos(nx)

Where x is the angle in radians along x axis

for x=0 , we see that the value of f(x) = 4

Hence acos(n*0)=4

           acos 0 = 4

           a *1 = 4    (as cos 0 = 1)

Hence we have a = 4 , therefore our equation becomes

f(x) = 4 cos (nx)

from the given graph we can see that

for x =   f(x) = -4

Hence

dividing both sides by 4 we get

Hence we have value of n also as 5

Hence our function is

f(x) =

$54.99

step-by-step explanation:

$54.99 includes 500 min. if she does not exceed 500 min then her bill is $54.99