🏆 ยอดนิยม: web//https://www.geeksforgeeks.org/c program find area triangle

Finding area using given sides:

Examples :

Input : a = 5, b = 7, c = 8
Output : Area of a triangle is 17.320508


Input : a = 3, b = 4, c = 5
Output : Area of a triangle is 6.000000

Area of a triangle can simply be evaluated using following formula.

Area = sqrt(s*(s-a)*(s-b)*(s-c))
where a, b and c are lengths of sides of
triangle and s = (a+b+c)/2

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

C++

// C++ Program to find the area  
// of triangle  
#include <bits/stdc++.h> 
using namespace std; 
  
float findArea(float a, float b, float c)  
{  
    // Length of sides must be positive  
    // and sum of any two sides  
    // must be smaller than third side.  
    if (a < 0 || b < 0 || c < 0 ||  
       (a + b <= c) || a + c <= b ||  
                       b + c <= a)  
    {  
        cout << "Not a valid trianglen";  
        exit(0);  
    }  
    float s = (a + b + c) / 2;  
    return sqrt(s * (s - a) *  
                    (s - b) * (s - c));  
}  
  
// Driver Code 
int main()  
{  
    float a = 3.0;  
    float b = 4.0;  
    float c = 5.0;  
  
    cout << "Area is " << findArea(a, b, c);  
    return 0;  
}  
  
// This code is contributed  
// by rathbhupendra 

C

#include <stdio.h>  
#include <stdlib.h>  
  
float findArea(float a, float b, float c) 
{ 
    // Length of sides must be positive and sum of any two sides 
    // must be smaller than third side. 
    if (a < 0 || b < 0 || c <0 || (a+b <= c) || 
        a+c <=b || b+c <=a) 
    { 
        printf("Not a valid trianglen"); 
        exit(0); 
    } 
    float s = (a+b+c)/2; 
    return sqrt(s*(s-a)*(s-b)*(s-c)); 
} 
  
int main() 
{ 
    float a = 3.0; 
    float b = 4.0; 
    float c = 5.0; 
  
    printf("Area is %f", findArea(a, b, c)); 
    return 0; 
} 

Java

// Java program to print 
// Floyd's triangle 
      
class Test 
{ 
    static float findArea(float a, float b, float c) 
    { 
        // Length of sides must be positive and sum of any two sides 
        // must be smaller than third side. 
        if (a < 0 || b < 0 || c <0 || (a+b <= c) || 
            a+c <=b || b+c <=a) 
        { 
            System.out.println("Not a valid triangle"); 
            System.exit(0); 
        } 
        float s = (a+b+c)/2; 
        return (float)Math.sqrt(s*(s-a)*(s-b)*(s-c)); 
    } 
          
    // Driver method 
    public static void main(String[] args)  
    { 
        float a = 3.0f; 
        float b = 4.0f; 
        float c = 5.0f; 
      
        System.out.println("Area is " + findArea(a, b, c)); 
    } 
} 

Python

# Python Program to find the area  
# of triangle  
  
# Length of sides must be positive  
# and sum of any two sides  
def findArea(a,b,c):  
  
    # must be smaller than third side.  
    if (a < 0 or b < 0 or c < 0 or (a+b <= c) or (a+c <=b) or (b+c <=a) ):  
        print('Not a valid trianglen')  
        return
          
    # calculate the semi-perimeter  
    s = (a + b + c) / 2
      
    # calculate the area  
    area = (s * (s - a) * (s - b) * (s - c)) ** 0.5
    print('Area of a traingle is %f' %area)  
  
  
# Initialize first side of traingle  
a = 3.0
# Initialize second side of traingle  
b = 4.0
# Initialize Third side of traingle  
c = 5.0
findArea(a,b,c)  
  
# This code is contributed by Shariq Raza  

C#

// C# program to print 
// Floyd's triangle 
using System; 
  
class Test { 
      
    // Function to find area 
    static float findArea(float a, float b, 
                        float c) 
    { 
          
        // Length of sides must be positive 
        // and sum of any two sides 
        // must be smaller than third side. 
        if (a < 0 || b < 0 || c <0 ||  
        (a + b <= c) || a + c <=b ||  
            b + c <=a) 
        { 
            Console.Write("Not a valid triangle"); 
            System.Environment.Exit(0); 
        } 
        float s = (a + b + c) / 2; 
        return (float)Math.Sqrt(s * (s - a) *  
                            (s - b) * (s - c)); 
    } 
          
    // Driver code 
    public static void Main()  
    { 
        float a = 3.0f; 
        float b = 4.0f; 
        float c = 5.0f; 
      
        Console.Write("Area is " + findArea(a, b, c)); 
    } 
} 
  
// This code is contributed Nitin Mittal. 

PHP

<?php 
function findArea($a, $b, $c) 
{ 
    // Length of sides must be positive 
    // and sum of any two sides must 
    // be smaller than third side. 
    if ($a < 0 or $b < 0 or
        $c < 0 or ($a + $b <= $c) or
        $a + $c <= $b or $b + $c <= $a) 
    { 
        echo "Not a valid trianglen"; 
        exit(0); 
    } 
    $s = ($a + $b + $c) / 2; 
    return sqrt($s * ($s - $a) *  
            ($s - $b) * ($s - $c)); 
} 
  
// Driver Code 
$a = 3.0; 
$b = 4.0; 
$c = 5.0; 
  
echo "Area is ", findArea($a, $b, $c); 
  
// This code is contributed anuJ_67. 
?> 

Output :

Area is 6

Finding area using coordinates:

If we are given coordinates of three corners, we can apply below Shoelace formula for area.

Area

 = | 1/2 [ (x₁y₂ + x₂y₃ + ... + x_n-1y_n + x_ny₁) -
           (x₂y₁ + x₃y₂ + ... + x_ny_n-1 + x₁y_n) ] |

C++

// C++ program to evaluate area of a polygon using 
// shoelace formula 
#include <bits/stdc++.h> 
using namespace std; 
   
// (X[i], Y[i]) are coordinates of i'th point. 
double polygonArea(double X[], double Y[], int n) 
{ 
    // Initialize area 
    double area = 0.0; 
   
    // Calculate value of shoelace formula 
    int j = n - 1; 
    for (int i = 0; i < n; i++) 
    { 
        area += (X[j] + X[i]) * (Y[j] - Y[i]); 
        j = i;  // j is previous vertex to i 
    } 
   
    // Return absolute value 
    return abs(area / 2.0); 
} 
   
// Driver program to test above function 
int main() 
{ 
    double X[] = {0, 2, 4}; 
    double Y[] = {1, 3, 7}; 
   
    int n = sizeof(X)/sizeof(X[0]); 
   
    cout << polygonArea(X, Y, n); 
} 

Java

// Java program to evaluate area of  
// a polygon usingshoelace formula 
import java.io.*; 
import java.math.*; 
  
class GFG { 
  
    // (X[i], Y[i]) are coordinates of i'th point. 
    static double polygonArea(double X[], double Y[], int n) 
    { 
        // Initialize area 
        double area = 0.0; 
      
        // Calculate value of shoelace formula 
        int j = n - 1; 
        for (int i = 0; i < n; i++) 
        { 
            area += (X[j] + X[i]) * (Y[j] - Y[i]); 
              
            // j is previous vertex to i 
            j = i;  
        } 
      
        // Return absolute value 
        return Math.abs(area / 2.0); 
    } 
      
    // Driver program  
    public static void main (String[] args)  
    { 
        double X[] = {0, 2, 4}; 
        double Y[] = {1, 3, 7}; 
  
        int n = X.length; 
        System.out.println(polygonArea(X, Y, n)); 
    } 
} 
  
  
// This code is contributed 
// by Nikita Tiwari. 

Python3

# Python 3 program to evaluate 
# area of a polygon using 
# shoelace formula 
  
# (X[i], Y[i]) are coordinates of i'th point. 
def polygonArea(X,Y, n) : 
  
    # Initialize area 
    area = 0.0
    
    # Calculate value of shoelace formula 
    j = n - 1
    for i in range( 0, n) : 
        area = area + (X[j] + X[i]) * (Y[j] - Y[i]) 
        j = i  # j is previous vertex to i 
      
      
    # Return absolute value 
    return abs(area // 2.0) 
  
    
# Driver program to test above function 
X = [0, 2, 4] 
Y = [1, 3, 7] 
  
n = len(X) 
print(polygonArea(X, Y, n)) 
  
  
# This code is contributed 
# by Nikita Tiwari. 

C#

// C# program to evaluate area of  
// a polygon usingshoelace formula 
using System; 
  
class GFG { 
  
    // (X[i], Y[i]) are coordinates  
    // of i'th point. 
    static double polygonArea(double []X, 
                       double []Y, int n) 
    { 
        // Initialize area 
        double area = 0.0; 
      
        // Calculate value of shoelace 
        // formula 
        int j = n - 1; 
        for (int i = 0; i < n; i++) 
        { 
            area += (X[j] + X[i]) *  
                        (Y[j] - Y[i]); 
              
            // j is previous vertex to i 
            j = i;  
        } 
      
        // Return absolute value 
        return Math.Abs(area / 2.0); 
    } 
      
    // Driver program  
    public static void Main ()  
    { 
        double []X = {0, 2, 4}; 
        double []Y = {1, 3, 7}; 
  
        int n = X.Length; 
        Console.WriteLine( 
                 polygonArea(X, Y, n)); 
    } 
} 
  
// This code is contributed by anuj_67. 

PHP

<?php 
// PHP program to evaluate area of a  
// polygon using shoelace formula 
  
// (X[i], Y[i]) are coordinates 
// of i'th point. 
function polygonArea( $X, $Y, $n) 
{ 
      
    // Initialize area 
    $area = 0.0; 
  
    // Calculate value of  
    // shoelace formula 
    $j = $n - 1; 
    for ( $i = 0; $i < $n; $i++) 
    { 
        $area += ($X[$j] + $X[$i]) *  
                 ($Y[$j] - $Y[$i]); 
                   
        // j is previous vertex to i 
        $j = $i;  
    } 
  
    // Return absolute value 
    return abs($area / 2.0); 
} 
  
    // Driver Code 
    $X = array(0, 2, 4); 
    $Y = array(1, 3, 7); 
    $n = count($X); 
    echo polygonArea($X, $Y, $n); 
  
// This code is contributed by anuj_67. 
?> 

Output :

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2019	2020	2021

Program to find area of a triangle

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

C++

C

Java

Python

C#

PHP

C++

Java

Python3

C#

PHP

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