文件目录

#include <iostream>
#include <cmath>
using namespace std;
double arctanx(double x)
{
    double s = 0, k;
    int d = 1;
    for (int i = 1; i < 1000000; i += 2)
    {
        k = pow(x, i) / i;
        if (k < 1e-6)
            break;
        s += d * k;
        d *= -1;
    }
    return s;
}
int main()
{
    printf("%.10lf", 6 * arctanx(1 / sqrt(3)));
    return 0;
}