Wikipedia talk:WikiProject Mathematics/Archive/2016/Oct

Edit war at geodesic
seems to believe that one of the formulas in geodesic needs an explicit summation, despite the article's explicit statement that it is using the Einstein summation convention. I have already reverted him several times. More eyes would be appreciated. Ozob (talk) 01:46, 1 October 2016 (UTC)


 * He has also been making extensive changes at Lagrangian mechanics and several other articles, changing notational conventions. See Special:Contributions/Dangvugiang. JRSpriggs (talk) 03:09, 1 October 2016 (UTC)

User:Latex-yow
I wanted to point out this users contributions, which seem to focus heavily on changing the math formatting of articles (sometimes in ways that are improvements, other times in ways that seem pointless). --JBL (talk) 13:11, 3 October 2016 (UTC)


 * Has there been an instance in which my edits have been negative? Pointless sometimes and improvements sometimes is certainly better than nothing, no? Latex-yow (talk) 15:47, 3 October 2016 (UTC)

Not technical enough
If ever an article needed a "Not Technical Enough" tag, here it is: Abel elliptic functions. Michael Hardy (talk) 02:54, 7 October 2016 (UTC)

Arithmetico-geometric sequence
Hello. A small question for you: I expected an "arithmetico-geometric sequence" to be a sequence of the form $$u_{n+1}=a u_n+b$$, but it turns out this only applies to French usage (disclaimer: I'm French), while in English the term Arithmetico-geometric sequence is already taken for something else. Fine. Why not. But then my questions are: 1° What in the world do you call sequences of the form I gave? I just can't seem to find anything to call them in English, and yet that's so simple and obvious an object that it surely must have a name! 2° Do they have a Wikipedia page yet? Compare Suite arithmetico-geometrique. &#123;&#123;u&#124;Gamall   &#125;&#125;  17:42, 12 October 2016 (UTC)
 * I am also French, and the only meaning of Arithmetico-geometric sequence (or Suite arithmetico-geometrique) I have heard before was a third meaning. It refers to the sequence of pairs (or intervals) whose limit is the arithmetic–geometric mean. Reliable sources are needed for clarifying the terminology. D.Lazard (talk) 18:11, 12 October 2016 (UTC)
 * I exhumed my old Terminale S math book; sequences of the form $$u_{n+1}=a u_n+b$$ are a staple of Bac problems (or were in the late 90s and early 00s; usually students are given a fixpoint w and asked to show that u_n - w is geometric, etc.), so I was sure to find the term there... annoyingly the book only ever says "suites du type $$u_{n+1}=a u_n+b$$". So maybe this terminology is not as universal as I thought. Regardless, such sequences probably deserve an article on the English Wikipedia, the problem is what to call it... &#123;&#123;u&#124;Gamall   &#125;&#125;  18:48, 12 October 2016 (UTC)
 * I have tested these terms on Google Scholar: "Arithmetic-geometric sequence": 46 hits; "Arithmetico-geometric": 371 hits; "Arithmetic-geometric mean": 7220 hits. This clearly supports my above comment. D.Lazard (talk) 21:17, 12 October 2016 (UTC)
 * In fact, the sequences considered in Suite arithmetico-geometrique are generally called linear recurrences of order 1. Note that Récurrence linéaire considers only the homogeneous case. D.Lazard (talk) 21:37, 12 October 2016 (UTC)

Linear recurrences: so that's where they were. I see that the fixpoint technique is dealt with in all generality there. That makes a lot of sense. I have added links to that article in the places where I'd have expected to find them. Thanks for clarifying that. &#123;&#123;u&#124;Gamall   &#125;&#125;  02:33, 13 October 2016 (UTC)

\bmod does not work.
I have created this.
 * \bmod does not work in Wikipedia's substitute for TeX. The "b" is supposed to mean "binary", and it should mean that the amount of space before and after "mod" is what is appropriate for a binary operator in mathematical notation. That space does not appear there.
 * \bmod does not work in Wikipedia's substitute for TeX. The "b" is supposed to mean "binary", and it should mean that the amount of space before and after "mod" is what is appropriate for a binary operator in mathematical notation. That space does not appear there.

Look at this section (Dominical letter). Michael Hardy (talk) 06:18, 15 October 2016 (UTC)
 * It looks OK to me $$x\bmod y$$. Whats your browser, OS and maths-preference setting? The help page Help:Displaying a formula suggests using   which creates a little extra space $$a\,\bmod\,b $$. --Salix alba (talk): 08:41, 15 October 2016 (UTC)
 * I see here "mod" and "bmod" ($$x\mod y$$ and $$x\bmod y$$) quite similar to this page. Boris Tsirelson (talk) 10:44, 15 October 2016 (UTC)
 * I compiled the Gregorian formula in Latex and got the same output as Wikipedia's (SVG, under Chrome linux). The spaces seem fine in both cases. Besides your settings, a screenshot of what you see (or directly the PNG or SVG file if that's what is produced for you) might be helpful. &#123;&#123;u&#124;Gamall   &#125;&#125;  12:34, 15 October 2016 (UTC)

It seems to miss the point to say you should code it as a\,\bmod\,b. Look at this:
 * $$ 5 + 3 \, $$
 * $$ +3 \, $$

In the second example you see less space to the right of the plus sign. That's how it's intended to work. It is for that reason that we prescribe the following for non-TeX math notation:
 * right: 5 + 3
 * wrong: 5+3
 * right: +3
 * wrong: + 3

\bmod is supposed to work like a binary operation symbol such as the plus sign, having some space to its left and right. To say that we have a manual that says we should manually add small spaces is to say "This thing doesn't work right, so you need to manually add small spaces to compensate for the bug." Michael Hardy (talk) 17:43, 15 October 2016 (UTC)

png file

 * It looks like you have the old PNG/texvc setup. Texvc is a very old unmaintained product and no one knows how to fix it. The best option is to change your preference to "MathML with SVG or PNG fallback", which I think is the default now. I suspect the spacing of \bmod has been a known bug for 10+ years and the  was a workaround to make it work. Now most people are using the MathML/SVG option it should not be necessary. --Salix alba (talk): 18:19, 15 October 2016 (UTC)

Here's another bug: These two lines look identical, whereas they should look different. In other words, \mathbin doesn't work.

\begin{align} & A \Delta B \\ & A \mathbin{\Delta} B \end{align} $$ Might this be the very same bug? Michael Hardy (talk) 18:24, 15 October 2016 (UTC)
 * Must be a different bug since the SVG backend fails, whereas it works correctly for \bmod. &#123;&#123;u&#124;Gamall   &#125;&#125;  18:29, 15 October 2016 (UTC)
 * I've created a new bug for   and  . --Salix alba (talk): 22:03, 15 October 2016 (UTC)

Does 'simple linear regression' imply OLS?
Should the definition of simple linear regression include the use of ordinary least squares (OLS) as the estimation technique, or does the term embrace non-OLS methods (e.g. least absolute deviations)? Interested editors may wish to respond at Talk:Simple linear regression. Qwfp (talk) 08:42, 18 October 2016 (UTC)

TeX not working
Why is most of the TeX code not getting rendered in this page? Michael Hardy (talk) 21:08, 20 October 2016 (UTC)
 * Works for me. What browser/OS are you using? --Izno (talk) 21:11, 20 October 2016 (UTC)
 * TeX seems intermittent for me too.  Sławomir Biały  (talk) 21:13, 20 October 2016 (UTC)
 * I too have observed that some TeX-heavy pages are half-rendered on occasion. I'm not sure it's specific to TeX, though; I'm only loading half the images of Bashar al-Assad right now, so it may be general sluggishness. Gamall Wednesday Ida (t.c) 23:18, 20 October 2016 (UTC)

The page returned to normal shortly after I posted this, but for something like a half hour it didn't work. Michael Hardy (talk) 00:45, 22 October 2016 (UTC)

Missing case in geometric series
On the page about Geometric Series, https://en.wikipedia.org/wiki/Geometric_series, for the finite series, the formula for the r<>1 case is given, but not the case for r=1. I believe the correct sum for r=1 is

s = an

Sorry, but I don't have the skills to do the edit myself. Thanks.

Griswold62 (talk) 13:06, 28 October 2016 (UTC)
 * @Griswold62: Why not. I have added that case. Gamall Wednesday Ida (t.c) 19:48, 28 October 2016 (UTC)


 * This discussion belongs on the talk page of Geometric series. I reverted the above edit and gave my reasons for doing so on that talk page. --Bill Cherowitzo (talk) 23:36, 28 October 2016 (UTC)

RFCs on citations templates and the flagging free-to-read sources
See Headbomb {talk / contribs / physics / books} 16:25, 29 October 2016 (UTC)
 * Village pump (proposals)
 * Village pump (proposals)