3.18 - Double, approximation of Pi

Objetive
Create a program to calculate an approximation for PI using the expression

pi/4 = 1/1 - 1/3 + 1/5 -1/7 + 1/9 - 1/11 + 1/13 ...

The user will indicate how many terms must be used, and the program will display all the results until that amount of terms.


Solution
using System;
public class Speed{
    public static void Main(){
    
        int terms;
        double result = 0;
        
        Console.WriteLine("PI estimator!");
        Console.Write("Enter the amount of terms to test: ");
        terms = Convert.ToInt32(Console.ReadLine());
        
        for (int i=1; i<=terms; i++)
        {
            int divisor = 2*i - 1;
            if (i%2 == 1) //  Odd term: positive
                result += 1.0f/divisor;
            else          //  Even term: negative
                result -= 1.0f/divisor;
            
            Console.WriteLine("To term {0}: {1}",
              i, 4*result);
        }
    }
        
}

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