Chapter 4 Exercise 4, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

(Geometry: area of a hexagon) The area of a hexagon can be computed using the following formula (s is the length of a side):$$Area=\frac{6s^2}{4\tan (\frac{\pi }{6}})$$Write a program that prompts the user to enter the side of a hexagon and displays its area.
Here is a sample run:

Enter the side: 5.5
The area of the hexagon is 78.59 

import java.util.Scanner;
 
 
public class ProgrammingEx4_4 {
 
 public static void main(String[] args) {
  Scanner input = new Scanner(System.in);
  System.out.print("Enter the side:");
 
  double s = input.nextDouble();
  double area = 6 * Math.pow(s, 2) / (4 * Math.tan(Math.PI / 6));
 
  area = Math.round(area * 100) / 100.0;
  System.out.println("The area of the hexagon is " + area);
 }
 
}