wow !
How can people ( is that you ?) find out this this expression/series for irrational numbers ?
we have
we can see that the series converges so quickly !
for this problem ,
I use a quite complicated method , is there any method better than mine ?
Go through it !
the general term of the seqence is
where
so the product of first
terms is
the series can be written in this form :
To evluate this series , we just need to create
next to the series .
I got
for
I got
or an elegant-appearance
the fifth term is about
, wow