割线法(Secant Method)求解f(x)=0

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

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

int main()
{
    double x1=0;
    double x2=1;
    double x = x2;
    while (fabs(f(x)) > 1e-6) {
        x = x2 - f(x2)*(x2-x1)/(f(x2)-f(x1));
        x1 = x2;
        x2 = x;
    }
    printf("solution for function exp(-x)-x=0 is %lf\n", x);
    return 0;
}