**Proposed exercise**

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.

**Output**

**Solution**

using System; public class ApproximationOfPI { public static void Main() { int n; double total = 0; Console.Write( "Enter the amount: " ); n = Convert.ToInt32(Console.ReadLine()); for (int i=1; i <= n; i++) { int divisor = 2 * i - 1; if ( i % 2 == 1 ) { total += 1.0f / divisor; } else { total -= 1.0f / divisor; } Console.WriteLine("Term {0}: {1}", i, 4 * total); } } }