# Double, approximation of Pi - Practice Exercises C# Sharp

## Lesson 3:

## Basic data types

## Exercise 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.

## Source Code:

```
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)
result += 1.0f / divisor;
else
result -= 1.0f / divisor;
Console.WriteLine("To term {0}: {1}",
i, 4 * result);
}
}
}
```

Exercisey
3.18