### Exercise

#### 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.

### Example Code

```
import java.util.*;
public class Main
{
public static void main(String[] args)
{
int terms;
double result = 0;
System.out.println("PI estimator!");
System.out.print("Enter the amount of terms to test: ");
terms = Integer.parseInt(new Scanner(System.in).nextLine());
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;
}
System.out.printf("To term %1$s: %2$s" + "\r\n", i, 4 * result);
}
}
}
```