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98 lines
3.5 KiB
Java
98 lines
3.5 KiB
Java
/*This is a Java Program to find the area of a triangle using determinant method.
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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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//This is a java program to find the area of triangle using method of determinants
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import java.util.Random;
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public class Area_Triangle_Determinants
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{
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public static double determinant(double A[][], int N)
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{
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double det = 0;
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if (N == 1)
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{
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det = A[0][0];
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}
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else if (N == 2)
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{
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det = A[0][0] * A[1][1] - A[1][0] * A[0][1];
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}
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else
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{
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det = 0;
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for (int j1 = 0; j1 < N; j1++)
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{
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double[][] m = new double[N - 1][];
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for (int k = 0; k < (N - 1); k++)
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{
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m[k] = new double[N - 1];
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}
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for (int i = 1; i < N; i++)
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{
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int j2 = 0;
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for (int j = 0; j < N; j++)
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{
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if (j == j1)
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continue;
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m[i - 1][j2] = A[i][j];
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j2++;
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}
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}
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det += Math.pow(-1.0, 1.0 + j1 + 1.0) * A[0][j1]
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* determinant(m, N - 1);
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}
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}
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return det;
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}
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public static void main(String args[])
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{
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Random random = new Random();
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int x1, x2, x3, y1, y2, y3;
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x1 = random.nextInt(10);
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x2 = random.nextInt(10);
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x3 = random.nextInt(10);
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y1 = random.nextInt(10);
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y2 = random.nextInt(10);
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y3 = random.nextInt(10);
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double[][] mat = new double[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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System.out
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.println("The matrix formed by the coordinates of the triangle is: ");
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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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System.out.print(mat[i][j] + " ");
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System.out.println();
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}
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double det = determinant(mat, 3) * 0.5;
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if (det < 0)
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System.out.println("The Area of the triangle formed by (" + x1
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+ "," + y1 + "), (" + x2 + "," + y2 + "), (" + x3 + ","
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+ y3 + ") = " + (det * -1));
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else
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System.out.println("The Area of the triangle formed by (" + x1
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+ "," + y1 + "), (" + x2 + "," + y2 + "), (" + x3 + ","
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+ y3 + ") = " + det);
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}
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}
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/*
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The matrix formed by the coordinates of the triangle is:
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3.0 4.0 1.0
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6.0 4.0 1.0
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3.0 9.0 1.0
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The Area of the triangle formed by (3,4), (6,4), (3,9) = 7.5 |