题目链接：https://noi.vip/problem/1026
求C++代码
将根号3分之一代入表达式。最后乘以6
#include <iostream>
using namespace std;
#include <iomanip>
#include <math.h>
double arctanx(double x)
{
double item = x,sum = x;
int n = 1,flag = 1;
do
{
flag *= -1;
item *= x*x;
n += 2;
sum += item * flag/ n;
}while(item / n >= 1e-6);
return sum;
}
int main()
{
cout<<fixed<<setprecision(10)<<6*arctanx(1.0/sqrt(3.0));
return 0;
}