29.13

#include <stdio.h>
#include <math.h>

#define size 4
void setNull(double array[][size])
{
    for(int i = 0 ; i != 4 ; ++i)
    {
        array[i][i] = 0;
    }
}

void print2dArray(double array[][size])
{
    for(int i = 0; i!= size ; ++i)
    {
        for(int j = 0 ; j != size; ++j)
        {
            printf("%.2lf ",array[i][j]);
        }
        printf("\n");
    }
}

int main()
{
    double array[size][size]= {{2,4,-6,7.4},
                         {4.5,-3,5,0},
                         {9.7,4.2,-3.8,2.75},
                         {3.3,-0.6,0,3.5}};

    setNull(array);
    print2dArray(array);

}