Aparallelogram with an equal base and height and an area greater than 64 square meters?

Acollege is planning to construct a rectangular parking lot on land bordered on one side by a highway. the plan is to use 680 feet of fencing to fence off the other three sides. what dimensions should the lot have if the enclosed area is to be a maximum?

Find the cosine function that is represented in the graph.

I’m stuck on this equation, anyone got the answer?