Question

How to calculate the determinant of a 3X3 matrix in C

Answer 1

#include <stdio.h> 

#define SIZE 3

int main(void)
{   
    float arr[SIZE][SIZE] = { {6, 1, 1}, {4, -2, 5}, {2, 8, 7} };
    
    /* 
     *       a b c
     * arr = d e f
     *       g h i
     * 
     * determinant = a*(e*i - f*h) - b*(d*i-f*g) + c*(d*h - e*g)
     * 
     */ 
    
    float determinant = arr[0][0] * (arr[1][1]*arr[2][2] - arr[1][2]*arr[2][1]) -
                        arr[0][1] * (arr[1][0]*arr[2][2] - arr[1][2]*arr[2][0]) +
                        arr[0][2] * (arr[1][0]*arr[2][1] - arr[1][1]*arr[2][0]);

    printf("%.2f", determinant);
          
    return 0;
}

  
/*
run:
    
-306.00

*/

 

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