Chapter 4, Problem 1PE

(Geometry: area of a pentagon) 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 $\text{Area}=\frac{5\times s^2}{4\times \text{tan}\left(\frac{\pi }{5}\right)}\text{'}\text{where }s$ is the length of a side. The side can be computed using the formula $s=2r\sin \frac{\pi }{5},\text{where }r$ is the length from the center of a pentagon to a vertex. Round up two digits after the decimal point.