Talk:Pi

Individual digits

On article there is equation for calculation of individual digits. I'm not sure about this because none of terms in sum has finite decimal representation, and I think hexadecimal representations are also infinite. So I think that to find digit N we must find Nth digit in first term, Nth digit in second term,...,Nth digit in (N-1)th term, and remainders from further digits. Because of this I think this method isn't to effective, but one simpler ones. This is rather question about mistake in my thinking, not any proof Wojowu (talk) 17:32, 3 January 2012 (UTC)

I haven't investigated, but have you looked at the source of the formula? A very cursory skim through it suggests that whatever infinite series result, you can cut them off eventually when the terms get too small. Leonxlin (talk) 04:34, 7 January 2012 (UTC)

Edit request on 7 January 2012

I was going to type that computers are still trying to get a non repeating number

Jcarcerano (talk) 03:22, 7 January 2012 (UTC)

Do you have a source to cite for that? Ian.thomson (talk) 03:27, 7 January 2012 (UTC)

And what do you mean? pi was proven to be non-repeating centuries ago. PrimeHunter (talk) 03:37, 7 January 2012 (UTC)

 Not done: per above. --Bryce (talk | contribs) 07:42, 7 January 2012 (UTC)

Edit request on 20 January 2012

Please add a link for "Ramanujan" (a mathematician who is mentioned in this article): there is a wikipedia page for him. http://en.wikipedia.org/wiki/Srinivasa_Ramanujan Eternal fizzer (talk) 12:24, 20 January 2012 (UTC)

 Done, thanks. He's now linked in two distant sections in this article. Adrian J. Hunter^{(talk•contribs)} 12:57, 20 January 2012 (UTC)

In 1706 John Machin was the first ...

In the paragraph that starts, "In 1706 John Machin was the first ...", I find it perplexing that Machin attempts to compute π based on 4atan(1/5)-atan(1/239) when π/4 = atan(1). Surely, if he were sophisticated to do what is said, he should have known of the simpler formula. Ksn (talk) 16:07, 15 February 2012 (UTC)

The article says:

In 1706 John Machin was the first to compute 100 decimals of π, using the arctan series in the formula

${\frac {\pi }{4}}=4\,\arctan {\frac {1}{5}}-\arctan {\frac {1}{239}}\!$

with

$\arctan \,x=\sum _{k=0}^{\infty }{\frac {(-1)^{k}x^{2k+1}}{2k+1}}=x-{\frac {x^{3}}{3}}+{\frac {x^{5}}{5}}-{\frac {x^{7}}{7}}+\cdots .\!$

The above arctan formula converges very slowly for x = 1 so using the formula for atan(1) is useless to compute many decimals of π. Compare x⁷/7 for x = 1/5 and for x=1. Then consider how many terms are needed before x^2k+1/(2k+1) becomes smaller than 1/10¹⁰⁰, corresponding to getting around 100 correct decimals of pi. Computers would never be able to get anywhere near it. PrimeHunter (talk) 21:10, 16 February 2012 (UTC)

Thank you! Ksn (talk) 15:36, 20 February 2012 (UTC)

3.14+

pi is not just 3.14 but can go on forever the numbers never end — Preceding unsigned comment added by 122.106.54.73 (talk) 00:45, 29 February 2012 (UTC)

Featured article?

I'm planning on working on the article, with the ultimate goal of reaching WP:FA status. I've gotten a few books from the library, including π: A biography of the world's most mysterious number (by Posametier & Lehmann); and Pi Unleashed (by Arndt and Haenel). The article is already in decent shape (and is already GA status), with some great illustrations. The biggest jobs appear to be (1) ensuring that all material has a good source, per WP:V; and (2) ensuring that the article is comprehensive. Plus, making sure the prose is professional quality (not my strong suit). Any help, suggestions, sources, etc. would be appreciated. --Noleander (talk) 21:08, 8 March 2012 (UTC)

I see there has been considerable discussion in the past about "π" vs "pi" for the article title. Apparently the current consensus is "pi" for the title, but "π" within the prose. I'm fine with that. But if anyone has any comments in that regard, or if they think it could impact FA, please speak up. --Noleander (talk) 22:08, 8 March 2012 (UTC)

the in popular culture section would probably need some tightening up. AIRcorn (talk) 00:37, 9 March 2012 (UTC)

Yeah, the reviewers at WP:FAC probably don't look too highly on that. I'm loath to delete cited material ... but maybe I can spin-off a subarticle per WP:SPINOFF; or move some material into footnotes. In any case, the section should be rather tight. --Noleander (talk) 01:12, 9 March 2012 (UTC)

You don't need to delete it all, it is probably one of the few articles where a popular culture section is justified. Personally I would just keep it to instances where the mention or use of Pi is a significant part of the media. In most of the films/TV shows it is used simply as a, sometimes minor, plot device. If there is no secondary source mentioning its use then it is probably not notable enough to include. You can always create the Pi in popular culture article as a last resort. AIRcorn (talk) 01:38, 9 March 2012 (UTC)

"Pi" is for text and titles, "π" is for formulas. See Britannica, Columbia, Wolfram's MathWorld, Mathematics, MacMillan Dictionary, Collins English Dictionary, Oxford Dictionaries, Merriam Webster, and American Heritage. It's the usual practice to spell out Greek letters: Chi-squared distribution, Dirac delta function, gamma function, Omega constant and so on. Kauffner (talk) 01:22, 9 March 2012 (UTC)

Thanks for the input. I notice the article uses π everywhere in the prose (not just formulas). Since that is the status quo, my inclination is to leave it alone (since it has already been brought up in the Talk pages in the past, and the status quo should be maintained absent a compelling reason). Personally, I have no strong preference one way or another. If anyone wants to propose a new convention (e.g. "pi" when not in a formula) the best path is to do an RfC. --Noleander (talk) 01:32, 9 March 2012 (UTC)