# Program to find area of a 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```

## C

```#include <stdio.h>
#include <stdlib.h>

float findArea(int a, int b, int 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);
}
int s = (a+b+c)/2;
return sqrt(s*(s-a)*(s-b)*(s-c));
}

int main()
{
int a  = 3;
int b = 4;
int c = 5;

printf("Area is %f", findArea(a, b, c));
return 0;
}```

## Java

```// Java program to print
// Floyd's triangle

class Test
{
static float findArea(int a, int b, int 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);
}
int s = (a+b+c)/2;
return (float)Math.sqrt(s*(s-a)*(s-b)*(s-c));
}

// Driver method
public static void main(String[] args)
{
int a = 3;
int b = 4;
int c = 5;

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
# Initialize second side of traingle
b = 4
# Initialize Third side of traingle
c = 5
findArea(a,b,c)

# This code is contributed by Shariq Raza
```

Output:
`Area is 6.000000`

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 + ... + xn-1yn + xny1) -
(x2y1 + x3y2 + ... + xnyn-1 + x1yn) ] |

```
```// 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);
}
```

Output :

`2`

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