In honor of Pi Day, here is a worksheet that calculates as many digits of pi as one might want.
Be sure to turn on the debugger and debugger window so you can see the result. You can also see how the calculation slows down as more terms are added.
The program uses the Taylor series expansion of atan(x) for the following solution (by Machin) of pi:
Since pi is known to a trillion digits or more now, the worksheet has no real purpose other than amusement.