What does it mean to evaluate a function

I’m stuck on this i don’t understand.

Afarm is to be built in the shape of quadrilateral abcd, as shown below. all four sides are equal. a rhombus abcd is shown with diagonal ac equal to 15.5 feet and diagonal bd equal to 13.2 feet. what is the area of the farm? pleas only pick from the 4 below 62 square feet 52.8 square feet 57.4 square feet 102.3 square feet

The angle of elevation from point a to the top of a cliff is 38 degrees . if point a is 80 feet from the base of the cliff , how high is the cliff ?