解平方根

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#define elsp 0.005
void calculation(double lg,double x)
{
    double ng=0;
    ng=0.5*(lg+x/lg);
    if(fabs(ng-lg)>=elsp){
      calculation(ng,x);
    }
    else printf("ans : %.2lf",ng);
}
int main()
{
    double x,lg=1.0;
    printf("please input a number : ");
    scanf("%lf",&x);
     calculation(lg,x);
    return 0;
}