long_kutar.cpp

分段算法的程序

#include<iostream.h>
#include<math.h>
#include<iomanip.h>

double f(double x,double y);
double f(double x,double y)
{
	double w;
	w=y-2*x/y;
	return w;
}

void main()
{
	double x,x1,y,y1,y2,k1,k2,k3,k4,h;
	int i,n;
	cout<<"请输入x,y和h的值："<<endl;
	cout<<"x=";
	cin>>x;
	cout<<"y=";
	cin>>y;
	cout<<"h=";
	cin>>h;
	n=(y-x)/h;
	cout<<"n="<<n<<endl;
	for(i=1;i<=n;i++)
	{
		x1=x+h;
		k1=f(x,y);
		k2=f(x+0.5*h,y+0.5*h*k1);
		k3=f(x+0.5*h,y+0.5*h*k2);
		k4=f(x+h,y+h*k3);
		y1=y+(k1+2*k2+2*k3+k4)*h/6;
		x=x1;
		y=y1;
		y2=sqrt(1+2*x);
		cout<<"x="<<x<<setw(8)<<"y="<<setprecision(6)<<y1<<setw(8)<<"y*="<<setprecision(6)<<y2<<endl;
	}
}