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