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

long double fkt1(long double x)
{
    return logl(x);
}

long double d(long double x, int k, int fkt)
{
    int i;
    long double h=1.0L;
    for(i=1;i<=k;i++) h=h/10;

    printf("h:%1.20Lf\n",h);
    printf("erst: %1.40Lf\n",fkt1(x+h));
    printf("zweit:%1.40Lf\n",fkt1(x));

    return (fkt1(x+h)-fkt1(x))/h;
}

int main()
{
    int i;
    assert(  __STDC_VERSION__ >= 199901L );

    for(i=1;i<=20;i++)
    {
        printf("%i: ",i);
        printf("d: %1.40Lf\n\n",d(1.6L,i,1));
    }

    return 0;
}