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

int
main ()
{
  double z,x,xplus;

  x = 1e-10;
  z = x - x*x/2.0 + x*x*x/3.0;
  printf ("z esatto:    %20.18lg\n", z);

  z = log (1.0 + x);
  printf ("z calcolato: %20.18lg\n", z);

  xplus = x + 1.0;
  z = x*log(xplus)/(xplus - 1.0);
  printf ("z algor. 2:  %20.18lg\n", z);
}