xian.c

我自己写的数值分析课程设计的算法

#include<stdio.h>
#include<math.h>

#define  TOL    1E-11
#define  NO     10

double f(double x)
{
	return exp(x)-3*x*x;
}

void main()
{
	FILE *file;
	double x_0 = 3.0;
	double x_1 = 4.0;
	double y_0 = f(x_0);
	double y_1 = f(x_1);
	double x = 0;
	double e = 0;
	int i = 2;
	file=fopen("xian.txt","w");
	
	while(i<NO)
	{
		x = x_1-y_1*(x_1-x_0)/(y_1-y_0);
		e = fabs(x-x_1);
		if(e<TOL)
		{
			fprintf(file,"根为 x = %.15Lg\n",x);
		}
		i = i+1;
		x_0 = x_1;
		y_0 = y_1;
		x_1 = x;
		y_1 = f(x);
	}
	fprintf(file,"method failed after %d iterations.\n",NO);
}