HW2.21

 import java.util.Scanner;

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

         System.out.print("Enter three points for a triangle: ");
         double x1 = input.nextDouble();
         double y1 = input.nextDouble();
         double x2 = input.nextDouble();
         double y2 = input.nextDouble();
         double x3 = input.nextDouble();
         double y3 = input.nextDouble();

         input.close();

         double side1Square = (x3 - x2) * (x3 - x2) + (y3 - y2) * (y3 - y2);
         double side1 = Math.pow(side1Square, 0.5);
         double side2Square = (x3 - x1) * (x3 - x1) + (y3 - y1) * (y3 - y1);
         double side2 = Math.pow(side2Square, 0.5);
         double side3Square = (x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1);
         double side3 = Math.pow(side3Square, 0.5);

         double s = (side1 + side2 + side3) / 2;
         double areaSquare = s * (s - side1) * (s - side2) * (s - side3);
         double area = Math.pow(areaSquare, 0.5);
         System.out.println("The area of the triangle is " + area);
     }
 }