#include <stdio.h>
#include <math.h>
/* richard.c : 1999 3 2 by Y.Yamazaki and T.Oguni */
double diff(double (*f)(), double x, double h)
{ return ((*f)(x+h)-(*f)(x-h))/(2.0*h); }
double richard(double (*f)(), double x, double h){
  double a,b,c,d;
  a=f(x+h/2.0);
  b=f(x+h)/8.0;
  c=f(x-h/2.0);
  d=f(x-h)/8.0;
  return (a-b-c+d)/(h*(1.0-(1.0/4.0)));
}
double func(double x){ return x*sin(x); }
double func1(double x){ return sin(x)+x*cos(x); }
main(){
  int i;
  double x, h=0.1;
  printf(" x\t f'(x)\t 通常\tリチャ−ドソン\n");
  for (i=0, x=0.2; i<4; i++, x+=0.2){
    printf("%.4f\t%.4f\t%.4f\t%.4f\n",x,func1(x),diff(func,x,h),richard(func,x,h));
  }
}