HW5.35

 import java.util.Scanner;

 public class Solution
 {
     public static void main(String[] args)
     {
         Scanner input = new Scanner(System.in);

         System.out.print("Enter the length of side: ");
         double side = input.nextDouble();

         input.close();

         System.out.println(getArea(side));
     }

     public static double getArea(double side)
     { return 5 * side * side / ( 4 * Math.tan(Math.PI / 5)); }
 }