C++ Programming Code Examples C++ > Computer Graphics Code Examples Program to Compute the Area of a Triangle Using Determinants Program to Compute the Area of a Triangle Using Determinants Formula for the area of a triangle using determinants x1 y1 1 Area=±1/2 x2 y2 1 x3 y3 1 The plus/minus in this case is meant to take whichever sign is needed so the answer is positive (non-negative). Do not say the area is both positive and negative. #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; }