# Calculating the 10,000+1 digits of π

The below program I developed to calculate the first 10,000 digits of π. This is C# and using  `BigInteger` class.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using System.Text;

namespace PrintPI
{
class Program
{
static void Main(string[] args)
{
//Console.WriteLine(2 * F(1));
string lines = GetPi(10000, 100).ToString();
int nInterval = 50;
string res = String.Concat(lines.Select((c, i) => i > 0 && (i % nInterval) == 0 ? c.ToString() + Environment.NewLine : c.ToString()));
Console.WriteLine(GetPi(10000,100).ToString());
System.IO.File.WriteAllText(@”C:UsersIsham MohamedDesktopPI.txt”, res);
}

public static BigInteger GetPi(int digits, int iterations)
{
return 16 * ArcTan1OverX(5, digits).ElementAt(iterations)
4 * ArcTan1OverX(239, digits).ElementAt(iterations);
}

//arctan(x) = x – x^3/3 + x^5/5 – x^7/7 + x^9/9 – …
public static IEnumerable<BigInteger> ArcTan1OverX(int x, int digits)
{
var mag = BigInteger.Pow(10, digits);
var sum = BigInteger.Zero;
bool sign = true;
for (int i = 1; true; i += 2)
{
var cur = mag / (BigInteger.Pow(x, i) * i);
if (sign)
{
sum += cur;
}
else
{
sum -= cur;
}
yield return sum;
sign = !sign;
}
}
}
}
Here you can find the digits.