https://noi.vip/problem/1026求π

Question

题目链接：https://noi.vip/problem/1026
求C++代码

Answer 1

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;
}