You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
89 lines
2.4 KiB
C++
89 lines
2.4 KiB
C++
/*This is a C++ program to find the area of 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;
|
|
}
|
|
|
|
/*
|
|
|
|
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
|