What is the equation of the graph below?

The equation of the graph given is:

Step-by-step explanation:

Clearly from the graph of the function that is provided to us we see that the graph repeats itself after every 5π.

i.e. the period of the function is: 5π.

Now we will check in each of the given options whose period is 5π.

We know that the period of a cosine function of the type:

is given by:

1)

The period of this function is:

Hence, option: 1 is incorrect.

2)

The period of this function is:

Hence, option: 2 is incorrect.

4)

The period of this function is:

Hence, option: 4 is incorrect.

3)

The period of this function is:

        Hence, option: 3 is the correct option.

check the picture below.

step-by-step explanation:

wrgasadvauoyfaiua-00uhf