777.txt

数学中用牛顿迭代公式

//5.牛顿迭代公式，求方程的近似解

//C/C++ code
#include<stdio.h>
#include<math.h>
#include<conio.h>
#define N 100
#define PS 1e-5
#define TA 1e-5
float Newton(float (*f)(float),float(*f1)(float),float x0 )
{
float x1,d=0;
int k=0;
do
{ 
   x1= x0-f(x0)/f1(x0);
   if((k++>N)||(fabs(f1(x1))<PS))
   {
    printf("\nFailed!");
    getch();
    exit();
   }
   d=(fabs(x1)<1?x1-x0:(x1-x0)/x1);
   x0=x1;
   printf("x(%d)=%f\n",k,x0);
}
while((fabs(d))>PS&&fabs(f(x1))>TA) ;
return x1;
}
float f(float x)
{
return x*x*x+x*x-3*x-3;
}
float f1(float x)
{ 
return 3.0*x*x+2*x-3;
}
void main()
{ 
float f(float);
float f1(float);
float x0,y0;
printf("Input x0: ");
scanf("%f",&x0);
printf("x(0)=%f\n",x0);
y0=Newton(f,f1,x0);
printf("\nThe root is x=%f\n",y0);
getch();
}