On 17 Feb, 2008, at 3:38 PM, Robert Purves wrote: > > Machin's formula is historically important in a specialised and > futile realm of human endeavour: > <http://en.wikipedia.org/wiki/William_Shanks> > <http://en.wikipedia.org/wiki/Pi#Calculating_.CF.80> An interesting bit of history, that, and thanks! It's a bit hard to imagine chewing through the numbers to get a hundred digits (or 527) of π, by hand! And then the poor sods who filled books with trig. and log. tables. But the question remains: what's to be gained by using that (or any) formula, rather than storing a constant? Anything, assuming you don't need 100 digit accuracy? Surely futility has more virulent forms than spending your Sunday afternoon calculating n digits of π? Or does it? Filling out an income tax return springs to mind. -- Ted -- Time is Nature's way of keeping everything from happening at once.