newton.cpp

牛顿迭代法求根 这个也是计算方法中的常用计算程序 学过的人都知道的

// newton.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include<iostream.h>
#include<math.h>
int main(int argc, char* argv[])
{
	double x0,x;
	double f(double x);
	double f1(double x);
	double newton(double f(double x),double f1(double x),double x0,int max=20);
	x0=2;
	x=newton(f,f1,x0);
	cout<<"x*x*x-2*x*x+x-12   The roof is:"<<x<<endl;
	cin.get();
	cin.get();
	return 0;
}
//原函数
double f(double x)
{
	return x*x*x-2*x*x+x-12;
};
//导函数
double f1(double x)
{ 
	return 3*x*x-4*x+1;
};
//牛顿切线法求根
double newton(double f(double x),double f1(double x),double x0,int max=20)
{
	int i,j;
	j=0;
	double x[50];
	i=0;
	x[0]=x0;
	for(i=0;i<max;i++)
	{
		x[i+1]=x[i]-f(x[i])/f1(x[i]);
		if((x[i+1]-x[i])<=0.00001  &&    (x[i+1]-x[i])>=-0.00001) break;
	};
	return x[i+1];
};