60.根据公式计算值

#define _CRT_SECURE_NO_WARNINGS
#include<math.h>
#include<stdio.h>
double fun(double eps)
{
double s, t;
int n = 1;
s = 0.0;
t = 1.0;
while (t >eps)
{
s += t;
t = t*n / (2*n + 1);
n++;
}
return(2*s);
}
int main()
{
double x;
printf("\nPlease enter a precision :");
scanf("%lf", &x);
printf("\neps=%lf ,Pi=%lf\n\n", x, fun(x));
getchar();
getchar();
return 0;
}