Write a program that prompts the user to enter the length from the center of a pentagon to a vertex and computes the area of the pentagon, as shown in the following figure.

The formula for computing the area of a pentagon is?

where s is the length of a side. The side can be computed using the formula s = 2r sin ?/5, where r is the length from the center of a pentagon to a vertex. Round up two digits after the decimal point. Here is a sample run:

5 x s? Area where 4 x tan