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# Area of a Triangle in the Cartesian Coordinate System

, 27 Oct 2012 CPOL
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For absolute beginners in Java

## Introduction

This is a simple Java class with a method to calculate the area, given the coordinates of the three nodes of the triangle, and a main method to invoke the calcArea method.

## Background

This is a just a class I've implemented in order to solve a problem in CodeCheff.com [ http://www.codechef.com/problems/NICEQUAD ]

since the other parts of the program are specific only to that problem, I thought to post this generic part -calculating the area of a triangle in a cartesian coordinate system- in Code Project. This is for absolute beginners to help themselves with:

• Getting input from the user
• Working with 2D arrays
• Using methods in Math class
• Rounding off a decimal number
• and anything new according to your level as a programmer...

## Using the code

Nothing complex here. Just compile and run as usual.

```/* Author: @TharieHimself */
import java.util.Scanner;
public class Triangle{

public void calcArea(){
Scanner scan = new Scanner(System.in);

int[][] coordinates = new int[3][2];
double[] sides = new double[3];
int count = 0;

for(int r=0; r<3; r++)
{
for(int c=0; c<2;c++){
count++;
System.out.print("Enter Coordinate "+count+": ");
coordinates[r][c] = scan.nextInt();
}
}

for(int i = 0; i<3; i++)
{
sides[i] = Math.sqrt((Math.pow((coordinates[i][0]- coordinates[(i + 1) % 3][0]), 2)) + Math.pow((coordinates[i][1] - coordinates[(i + 1) % 3][1]), 2));
}

double s = (sides[0]+ sides[1]+ sides[2])/2;
double area = Math.sqrt(s*(s-sides[0])*(s-sides[1])*(s-sides[2]));

/* THIS WILL ROUND OFF THE AREA TO THREE DECIMAL PLACES */
double roundOff = Math.round(area * 1000.0) / 1000.0;

if(area <= 0)
System.out.println("\nYour Triangle does not exist!");
else
System.out.println("\nArea of your Triangle is: "+roundOff);

}

}
```

## Points of Interest

A formula for calculating the area of a triangle when all sides are known is attributed to two famous mathematicians; Heron of Alexandria and Archimedes!

## License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

## About the Author

 Sri Lanka
No Biography provided

## Comments and Discussions

 First Prev Next
 No need to use Pow or Sqrt Andreas Gieriet27-Oct-12 5:39 Andreas Gieriet 27-Oct-12 5:39
 It can be done. rhuiden26-Oct-12 12:03 rhuiden 26-Oct-12 12:03
 Re: It can be done. Tharindu Wijeratna26-Oct-12 16:41 Tharindu Wijeratna 26-Oct-12 16:41
 Keep it simple, sir Daniele Alberto Galliano26-Oct-12 3:39 Daniele Alberto Galliano 26-Oct-12 3:39
 Last Visit: 31-Dec-99 19:00     Last Update: 25-Nov-15 4:39 Refresh 1

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