## October 2008 riddle

This cute little riddle was brought to my attention only very recently, but it immediately became an instant favorite with me. I'll give credits for its origin on the answer page.

The riddle concerns the number . The question is this: what is this number's 48th digit after the decimal point?

To be sure, one can solve this riddle with any calculator that has enough precision digits, but the point here is to solve it using your head. Answers will only be accepted if they entail a derivation proving what the required digit is, without requirng any arithmetic that one cannot perform easily in one's head.

Readers who wish to really enjoy this one will do well to avoid any use of calculators in approaching the riddle.

### List of solvers:

Bojan Bašić (1 October 11:45)
Xiaohui Bei (1 October 16:04)
Hongcheng Zhu (1 October 18:16)
Dan Dima (2 October 00:20)
Li Wei (2 October 00:23)
Lu Sida (4 October 21:16)
Wolfgang Kais (5 October 09:44)
Mark Tilford (7 October 08:02)
MyongHun Jo (8 October 03:16)