#include <stdio.h>
#include <math.h>
/*
set logscale x
set logscale y
plot "deriv.dat" pt 5 ps 2,x*x lc 0
*/
double f(double x){
    return 1000000000.0+sqrt(x);
}
double df(double x){
    return 1/(2*sqrt(x));
}
double Eh(double x,double h){
    return fabs((f(x+h)-f(x-h))/(2*h)-df(x));
}
int main(){
    double h=1;
    for(int i=0;i<20;i++){
        printf("%g %22.15e\n",h,Eh(2,h));
        h/=2;
    }
    return 0;
}