Code:
#include stdio.h
#include stdlib.h
#include iostream
#include math.h
using namespace std;
double det(int n, double mat[3][3])
{
double submat[3][3];
float d;
for (int c = 0; c < n; c++)
{
int subi = 0; //submatrix's i value
for (int i = 1; i < n; i++)
{
int subj = 0;
for (int j = 0; j < n; j++)
{
if (j == c)
continue;
submat[subi][subj] = mat[i][j];
subj++;
}
subi++;
}
d = d + (pow(-1, c) * mat[0][c] * det(n - 1, submat));
}
return d;
}
int main(int argc, char **argv)
{
cout << "Enter the points of the triangle:\n";
int x1, x2, x3, y1, y2, y3;
cin >> x1;
cin >> y1;
cin >> x2;
cin >> y2;
cin >> x3;
cin >> y3;
double mat[3][3];
mat[0][0] = x1;
mat[0][1] = y1;
mat[0][2] = 1;
mat[1][0] = x2;
mat[1][1] = y2;
mat[1][2] = 1;
mat[2][0] = x3;
mat[2][1] = y3;
mat[2][2] = 1;
cout << "\nMatrix formed by the points: \n";
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
cout << mat[i][j] << " ";
cout << endl;
}
float determinant = det(3, mat)*0.5;
if (determinant < 0)
cout << "The Area of the triangle formed by (" << x1 << "," << y1
<< "), (" << x2 << "," << y2 << "), (" << x3 << "," << y3
<< ") = " << (determinant * -1);
else
cout << "The Area of the triangle formed by (" << x1 << "," << y1
<< "), (" << x2 << "," << y2 << "), (" << x3 << "," << y3
<< ") = " << determinant;
return 0;
}
Output:
Enter the points of the triangle:
3 4
6 4
3 9
Matrix formed by the points:
3 4 1
6 4 1
3 9 1
The Area of the triangle formed by (3,4), (6,4), (3,9) = 7.5
------------------
(program exited with code: 0)
Press return to continue
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