write a c programs to find the trace of a given matrix.

for an integer matrix,

int trace(int *a,int n) {
int t=0,i;
for (i=0;i<n;i++) {t += *(a[i*n+i])}
return t;
}

To find the trace of a given matrix in a C program, you can follow these steps:

1. Start by including the necessary header files:
```c
#include <stdio.h>
```

2. Declare the size of the matrix (assuming it is a square matrix) using a constant or read it from the user:
```c
#define SIZE 3
```

3. Declare a 2D array to store the matrix elements:
```c
int matrix[SIZE][SIZE];
```

4. Populate the matrix by reading the elements from the user or using any suitable method:
```c
printf("Enter the matrix elements:\n");
for (int i = 0; i < SIZE; i++) {
for (int j = 0; j < SIZE; j++) {
printf("Enter element at [%d][%d]: ", i, j);
scanf("%d", &matrix[i][j]);
}
}
```

5. Calculate the trace of the matrix by summing the diagonal elements:
```c
int trace = 0;
for (int i = 0; i < SIZE; i++) {
trace += matrix[i][i];
}
```

6. Finally, display the trace of the matrix:
```c
printf("Trace of the matrix is: %d\n", trace);
```

Putting it all together, here's the complete C program to find the trace of a given matrix:

```c
#include <stdio.h>

#define SIZE 3

int main() {
int matrix[SIZE][SIZE];

printf("Enter the matrix elements:\n");
for (int i = 0; i < SIZE; i++) {
for (int j = 0; j < SIZE; j++) {
printf("Enter element at [%d][%d]: ", i, j);
scanf("%d", &matrix[i][j]);
}
}

int trace = 0;
for (int i = 0; i < SIZE; i++) {
trace += matrix[i][i];
}

printf("Trace of the matrix is: %d\n", trace);

return 0;
}
```

You can modify the `SIZE` constant to match the size of your matrix. Remember to compile and run the program to see the trace of the given matrix.