Question

Write a program that prompts the user to enter three points (x1,

y1), (x2, y2), (x3, y3) of a triangle and displays its area.

The formula for computing the distance of two points (x1, y1) and (x2, y2) is

d = Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));

or

d = Math.pow((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1), 0.5);

The formula for computing the area of a triangle is

s = (side1 + side2 + side3) / 2.0;

area = Math.sqrt(s * (s - side1) * (s - side2) * (s - side3));

or

area = Math.pow(s * (s - side1) * (s - side2) * (s - side3), 0.5);

Here is a sample run:

Enter three points for a triangle: 1.5 -3.4 4.6 5.0 9.5 -3.4

The area of the triangle is 33.60.

Answer 1

Since you have not provided the language of your preference, I am providing the code in Java.

import java.util.Scanner;

public class tester {

   public static double getDistance(double x1, double y1, double x2, double y2) {

       return Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));

   }

  

  

   public static void main(String[] args) {

       double x1, y1, x2, y2, x3, y3;

       Scanner sc = new Scanner(System.in);

       System.out.print("Enter three points for a triangle: ");

       x1 = sc.nextDouble();

       y1 = sc.nextDouble();

      

       x2 = sc.nextDouble();

       y2 = sc.nextDouble();

      

       x3 = sc.nextDouble();

       y3 = sc.nextDouble();

      

       double side1 = getDistance(x1, y1, x2, y2);

       double side2 = getDistance(x2, y2, x3, y3);

       double side3 = getDistance(x3, y3, x1, y1);

      

       double s = (side1 + side2 + side3) / 2.0;

       double area = Math.sqrt(s * (s - side1) * (s - side2) * (s - side3));

      

       System.out.format("The area of the triangle is : %.2f", area);

      

      

   }

}