If you cannot read and write a trivial math equation as code then I really question how you got here. That formulation for approximation of irrationals is one of the reasons computers exist! If you can't do this, go into a cave on a mountaintop behind a waterfall in a hidden vale and proceed to train until you can. It's not an unreasonable or un-useful thing.

Of course, it's actually trickier than you might think on modern computers if you go out much further than 10 decimal places or so.