Question

What is the C programming code to find the inverse of a 2*2 matrix?

Answer 1

output:

CODE:

#include<stdio.h>
#include<math.h>
/* function declarations*/

float determinantvalue(float [][25], float);
void cofactorvalue(float [][25], float);
void transposematrix(float [][25], float [][25], float);
int main()
{
float arr[25][25], k=2, d;
int i, j;
printf("Enter the elements of %.0fX%.0f Matrix : \n", k, k);
for (i = 0;i < k; i++)
{
for (j = 0;j < k; j++)
{
scanf("%f", &arr[i][j]);
}
}
/* calling determinant function for det value finding*/
d = determinantvalue(arr, k);
if (d == 0)
printf("\nInverse matrix is not possible");
else
cofactorvalue(arr, k);
}

/*function for determinant value*/
float determinantvalue(float arr[25][25], float k)
{
float s = 1, det = 0, b[25][25];
int i, j, m, n, c;
if (k == 1)
{
return (arr[0][0]);
}
else
{
det = 0;
for (c = 0; c < k; c++)
{
m = 0;
n = 0;
for (i = 0;i < k; i++)
{
for (j = 0 ;j < k; j++)
{
b[i][j] = 0;
if (i != 0 && j != c)
{
b[m][n] = arr[i][j];
if (n < (k - 2))
n++;
else
{
n = 0;
m++;
}
}
}
}
det = det + s * (arr[0][c] * determinantvalue(b, k - 1));
s = -1 * s;
}
}

return (det);
}

void cofactorvalue(float num[25][25], float f)
{
float b[25][25], fac[25][25];
int p, q, m, n, i, j;
for (q = 0;q < f; q++)
{
for (p = 0;p < f; p++)
{
m = 0;
n = 0;
for (i = 0;i < f; i++)
{
for (j = 0;j < f; j++)
{
if (i != q && j != p)
{
b[m][n] = num[i][j];
if (n < (f - 2))
n++;
else
{
n = 0;
m++;
}
}
}
}
fac[q][p] = pow(-1, q + p) * determinantvalue(b, f - 1);
}
}
transposematrix(num, fac, f);
}
/*to find transpose of matrix*/
void transposematrix(float num[25][25], float fac[25][25], float r)
{
int i, j;
float b[25][25], inversematrix[25][25], d;
for (i = 0;i < r; i++)
{
for (j = 0;j < r; j++)
{
b[i][j] = fac[j][i];
}
}
d = determinantvalue(num, r);
for (i = 0;i < r; i++)
{
for (j = 0;j < r; j++)
{
inversematrix[i][j] = b[i][j] / d;
}
}
printf("\nThe inverse of matrix is : \n");
for (i = 0;i < r; i++)
{
for (j = 0;j < r; j++)
{
printf("\t%f", inversematrix[i][j]);
}
printf("\n");
}
}