# Wikipedia talk:WikiProject Mathematics/Archive 49

## Moves to inappropriate names?

Recently, Nbarth (talk · contribs) has moved some articles to new names which are inappropriate according to Wikipedia:Naming conventions. In particular, I noticed that he moved Lambert quadrilateral to Ibn al-Haytham–Lambert quadrilateral and Saccheri quadrilateral to Khayyam–Saccheri quadrilateral, saying "full term, credit original discoverer". JRSpriggs (talk) 13:52, 20 April 2009 (UTC)

Looking at the link, some of the moves did conform to the Wikipedia conventions, however some did not. In my opinion, it would be in the best interests of the user to notify him/her about the issue. --PST 13:58, 20 April 2009 (UTC)
OK. I left a message on his talk page. JRSpriggs (talk) 14:13, 20 April 2009 (UTC)

I think these are the wrong names for those articles and they should be moved back. This is English Wikipedia. Nbarth has argued that Wikipedia:Neutral_point_of_view#Article_naming is in conflict with naming convention guidelines but actually, that section of the NPOV policy explicitly states:

Where proper nouns such as names are concerned, disputes may arise over whether a particular name should be used. Wikipedia takes a descriptive rather than prescriptive approach in such cases, by using the common English language name as found in verifiable reliable sources. Where inanimate entities such as geographical features are concerned, the most common name used in English-language publications is generally used. See Wikipedia:Naming conflict for further guidance.

It couldn't be any clearer. Even Nbarth has stated the common English names are Lambert quadrilateral and Saccheri quadrilateral resp. --C S (talk) 01:02, 1 May 2009 (UTC)

I moved the pages back per the above reason. I have notified Nbarth to this discussion thread. --C S (talk) 01:08, 1 May 2009 (UTC)
I've also reverted Saccheri quadrilateral back to the previous version not only to revert the terminology but because I think it reads slightly better. Regarding the terminology issue, however, it's not appropriate for use to try and rectify historical wrongs by using terminology less likely to be familiar to the reader. Khayyam is actually given plentiful credit in the article (there's more on him than Saccheri). --C S (talk) 01:31, 1 May 2009 (UTC)

## Recursion

Resolved

Someone is once again adding circular links from recursion to itself. Could someone else deal with it this time? — Carl (CBM · talk) 14:43, 27 April 2009 (UTC)

It seems to have stopped after Carl reverted him Incidentally I don't see what's wrong with a little joke under the "see also" section, but I understand jokes aren't for everyone :-). --C S (talk) 01:16, 1 May 2009 (UTC)

## Euclidean algorithm at FAC

I have nominated Euclidean algorithm at FAC. Please consider reviewing the article. Thank you to the several mathematicians here who helped to improve the article over the past few weeks. It was much appreciated and the favor will be returned. Proteins (talk) 16:28, 27 April 2009 (UTC)

A gentle reminder to the mathematicians here that the Euclidean algorithm is still at FAC, and would benefit from their reviewing it. Several mathematicians have helped to improve the article (thanks, all!), but more reviewers would be welcome. Thank you, Proteins (talk) 15:27, 1 May 2009 (UTC)

## Another Weisstein neologism?

Please comment at Talk:Sexy prime#neologism.3F. --Trovatore (talk) 23:29, 3 May 2009 (UTC)

## Articles in need of attention/cleanup/something

Equipossible and Equiprobable could really need some help:

Equiprobability is a philosophical concept in probability theory that allows one to assign equal probabilities to outcomes that are judged to be equipossible or to be "equally likely" (in some sense).

Equiprobability "allows" one to assign probabilities? Etc. etc.

CRGreathouse (t | c) 17:27, 7 May 2009 (UTC)

I've nominated the article titled Loyer's paradox for deletion. I hesitated for a few weeks before doing this because the article's author had said he would replace the content. Some time has gone by with no progress on this. I'll withdraw the nomination if he can do that. But for now, see the discussion at Wikipedia:Articles for deletion/Loyer's paradox. Don't just say Keep or Delete; give your arguments for your position. Michael Hardy (talk) 00:27, 8 May 2009 (UTC)

## Treatment of tensors

Apparently there are nearly half a dozen articles treating tensors:

and maybe even more.

Besides the awful naming of these articles (what is 'classical' about the component treatment of tensors), is it in anyway useful? It seems to me that there must be a better way of organizing these articles. Any thoughts? (TimothyRias (talk) 11:21, 22 April 2009 (UTC))

Oh my gosh, this is awful. It looks like these are all content forks of the same material. Something has to be done with this. There's also a tensor product article which covers the same material again! What a mess. Ozob (talk) 15:11, 22 April 2009 (UTC)
It does seem like a lot of work to cobble all these articles together! On a hunch, I also noticed dyadic tensor, dyadics, symmetric tensor, antisymmetric tensor and pseudotensor. I've a soft spot for axiality and rhombicity since I published on that in protein NMR, but they should probably be integrated into another article as well. On the other hand, it might be good to separate tensor and tensor field. Proteins (talk) 17:57, 22 April 2009 (UTC)
I'm in full agreement. On top of the (mis)organisation of these articles, for instance the main tensor article is in quite bad shape. Can anyone get any view on what a tensor is from that one? I met this mess of articles more than a year ago, I think; what kept me from getting involved was that these articles seem to be subject of frequent and unproductive disputes. Tensors (in all their meanings) could be among those entities where the mathematical and (undergrad?) physical / engineering usage and customs are very far from each other. Full clean-up is in order, but could be resisted, I'm afraid. Stca74 (talk) 17:59, 22 April 2009 (UTC)

You know, this is a pretty old mess. I seem to recollect that there should be a simple, concrete article explaining basic tensor stuff like sum convention, raising/lowering indices, etc., without using abstract algebra. I don't know what happened to it (if it ever existed), but the "classical treatment" version is clearly inadequate. The problem seems to be that tensors are a subject that a wide variety of people are interested in reading about, undergrad engineers, people studying relativity, etc. Due to frequent complaining about articles being unreadable (understandable and justified in my view), some kind of compromise was arranged with different level articles. Unfortunately, the above organization doesn't seem to be how I remember things (some of "intermediate treatment" seems to have been at "classical treatment" before...). It might be worthwhile asking User:Kevin_Baas what happened; he's one of the few people, I think, that has been there through the entire history of these articles. --C S (talk) 18:30, 22 April 2009 (UTC)

From the standpoint of someone who learned tensors in order to study general relativity, I think that the Classical treatment of tensors is much easier to understand than the other articles. Also, you missed Tensor density, a closely related generalization. JRSpriggs (talk) 09:56, 24 April 2009 (UTC)
It might be easier to understand, but only because there's hardly anything there. That's why I call it inadequate. Not to mention, the only explanation of what's going on is the "abstract" one, talking about bundles and such. --C S (talk) 15:57, 24 April 2009 (UTC)
I don't understand why I "missed" that article, but thanks for bringing that to our attention. --C S (talk) 16:00, 24 April 2009 (UTC)
Also related are Covariant transformation and Covariance and contravariance of vectors.
To C S: Physicists and engineers do not care what a tensor really is, they only want to know how to use it. That is, how to transform them, add them, multiply them, etc.. For that purpose, the classical treatment (which I learned from one of Eddington's books on relativity) is quite sufficient. JRSpriggs (talk) 00:34, 1 May 2009 (UTC)
Yes, I understand what it is you're saying. But I wasn't saying that Eddington's treatment was insufficient. I think nobody could learn how to use tensors from classical treatment of tensors. --C S (talk) 00:37, 1 May 2009 (UTC)
I don't know what your comment about what tensors "really is" is in response to. What I said was that classical treatment of tensors doesn't give sufficient explanation of what is going on, only giving some abstractions. I didn't mean something abstract like "what tensors really are" (whatever that means), but rather I don't think sufficient explanation is given for engineers to understand their computations. Even engineers need to understand some basics of what they are computing, otherwise the computer would replace them. I seriously doubt any engineer is going to be able to work out any tensor computations after reading that article. It is considerably spare compared to the usual "how to use" treatments I have seen. --C S (talk) 00:41, 1 May 2009 (UTC)

Just a quick comment that Hamilton's ideas, and the quaternionists point of view, have somewhat of a claim on the right to share the tensor name space with those of the matrix algebra point of view. Tensor of a quaternion being an example of a defunked article on the subject.130.86.76.31 (talk) 23:24, 4 May 2009 (UTC)

The "mess" is largely caused by incompatible ideas of pedagogy in this area. Being a mathematician I would prefer to discuss what a tensor is, rather than what someone else thinks is the right way to teach tensors to the people he or she has to teach, for whatever purpose that will be. And I would argue that an encyclopedia (rather than a textbook) has an obligation to address that question. The social fact is that there were in the past plenty of people agitating for their version of a suitable pedagogy of tensor products to be in Wikipedia. Hence the forking. If anyone wants to re-run the whole discussion, go ahead; but I would be unsympathetic to involving certain people from the past of the article, and to hearing once more what the article ought to contain. These days we should ask for reliable sources, starting from the very definitions. Charles Matthews (talk) 22:11, 7 May 2009 (UTC)
Unfortunately I think you'll run into a lot of resistance insisting on what a tensor is. Classically, as far as I can tell tensors were treated as new primitive quantities that were not describable in terms of other quantities. What a tensor is (in this case, a section of a tensor product of tangent and cotangent bundles) was never specified; indeed, it couldn't be specified until the language of tensor products of vector bundles had been developed. As far as I can tell, this approach to tensors is still universal in engineering and the physical sciences. I have even heard a prominent applied mathematician say derogatory things about the incomprehensible way in which algebraists approach tensors.
My own view is that the main tensor article should begin with the history, and I mean a thorough history, not one that stops a little after 1900 like the present tensor article's history does. A thorough history would introduce both the viewpoint that a tensor is a quantity that transforms in a certain way as well as the viewpoint that a tensor is a section of a certain vector bundle; it would even mention that a tensor is in general an element of a tensor product of modules (or a section of a tensor product of sheaves). I think that gives a foundation to discuss all the aspects of tensors, classical, modern, or whatever. Ozob (talk) 17:10, 8 May 2009 (UTC)
Well, we do have content policies here, and they are not suspended when there is disagreement on the type of treatment. Rather, that is exactly the context where they should be brought into play. The normal view isn't that you start the article with a thorough history, because we believe in a 'concentric' treatment. We don't make the article group (mathematics) start with a history that has to include the odd order theorem; we start with information about what a group is, and why groups matter in mathematics, as well as some relevant history.
It is also valid to bring into the discussion what other encyclopedias do. The big Soviet encyclopedia, the basis of the Springer encyclopedia, has articles: tensor algebra, tensor analysis, tensor bundle, tensor calculus, tensor density, tensor on a vector space, tensor product. As well as related ones such as multilinear algebra. The Japanese Encyclopedic Dictionary of Mathematics takes a different approach, with one main article tensor calculus from a differential geometer's point of view, but about 50 different sections in articles spread over the encyclopedia treating different aspects of tensors. Neither of those models starts with the assumption that a 'killer' article is the ideal.
By the way, bringing up sniping of applied mathematicians is about as unhelpful a comment as can be made here. There is the whole traditional pedagogic issue of 'methods of mathematical physics' courses. (I learned tensors, if you could call it that, from Eddington and then a DAMTP treatment following Jeffreys.) But that is not for here. Anyone who wants to write 'methods' material can do a wikibook that way. The mission statement for Wikipedia is clear: articles about tensors compile verifiable facts about tensors. Charles Matthews (talk) 19:03, 8 May 2009 (UTC)

## Algorithmic Lovász local lemma

The new article titled Algorithmic Lovász local lemma has no introductory section. This raises two questions:

• Can someone do something about it?
• I thought there was a template for such occasions. Where is it?

Michael Hardy (talk) 04:21, 9 May 2009 (UTC)

Template:Intro-missing? --El Caro (talk) 11:30, 9 May 2009 (UTC)
I've added that template—thank you. Michael Hardy (talk) 17:08, 10 May 2009 (UTC)

## GAR for Rubik's Cube

The article Rubik's Cube is tagged as being a part of this WikiProject, so I am letting the members know that I have started a Good Article Reassessment as part of the GA Sweeps process. You can find a list of my concerns on the article's talk page. Thanks and good luck! Nikki311 00:39, 13 May 2009 (UTC)

## PlanetMath

Just to let you know, looks like the PlanetMath undergoes an extensive editing. If so, the more eyes the better... ptrf (talk) 13:08, 14 May 2009 (UTC)

Amazing. After about 80 edits by Bci2, the article seems to have undergone absolutely no improvement. Quite the contrary. --C S (talk) 14:10, 14 May 2009 (UTC)

## TeX question

\begin{align} \frac{1}{N_e^{(F)}} = \frac{1}{4T}\left\{\frac{1}{N_0^f}+\frac{1}{N_0^m} \right. & {} + \sum_i\left(\ell_{i+1}^f\right)^2\left(v_{i+1}^f\right)^2\left(\frac{1}{\ell_{i+1}^f}-\frac{1}{\ell_i^f}\right) \\ & \left. {} + \sum_i\left(\ell_{i+1}^m\right)^2\left(v_{i+1}^m\right)^2\left(\frac{1}{\ell_{i+1}^m}-\frac{1}{\ell_i^m}\right) \right\}. \end{align}

The sizes of the left and right curly braces above do not match, and in fact, the one on the left isn't big enough for the last set of fractions on the first line. Can something be done about this while retaining the format the breaks the whole display into two lines? Michael Hardy (talk) 11:11, 14 May 2009 (UTC)

Is this what you want?
\begin{align} \frac{1}{N_e^{(F)}} = \frac{1}{4T}\left\{\frac{1}{N_0^f}+\frac{1}{N_0^m} {} + \sum_i\left(\ell_{i+1}^f\right)^2\left(v_{i+1}^f\right)^2\left(\frac{1}{\ell_{i+1}^f}-\frac{1}{\ell_i^f}\right)\right. \;\;\, & \\ \left. {} + \sum_i\left(\ell_{i+1}^m\right)^2\left(v_{i+1}^m\right)^2\left(\frac{1}{\ell_{i+1}^m}-\frac{1}{\ell_i^m}\right) \right\}. & \end{align}
--Hans Adler (talk) 12:07, 14 May 2009 (UTC)
That seems to do it. I've now used (approximately) that format in effective population size.
Thank you, Hans. Michael Hardy (talk) 11:20, 16 May 2009 (UTC)
Normally you would use \vphantom, by inserting
\vphantom{\sum_i\left(\frac{1}{P_1^f}\right)}
inside the first set of delimiters. However, this does not work with Mediawiki's tex engine; the vphantom command is not recognized. So you must either set the sizes manually (big, bigg, etc) or use an alignment hack like Hans suggests. — Carl (CBM · talk) 13:19, 14 May 2009 (UTC)

## Template:SpecialChars

There is an edit war brewing at convolution over the placement of the {{SpecialChars}} template. There seems to be no precedent for placing this at the top of maths articles, and there is no editing guideline as far as I can tell either — certainly nothing at WP:MOSMATH. My chief objection is that the template is ugly and pushes the meaningful content further down the page. Sławomir Biały (talk) 12:34, 15 May 2009 (UTC)

In general I do not think we need to use this template on math articles at all. Perhaps if the special characters were unexpected, it would help, but for a math article people should expect them. — Carl (CBM · talk) 10:39, 16 May 2009 (UTC)

## Strange page

János Komlós is, as of a few minutes ago, a disambiguation page. Before that, it said this:

János Komlós is an American mathematician, working in probability theory, discrete mathematics. He is a professor at the Rutgers University.
He was also (Budapest, 9 February, 1922–Budapest,18 July, 1980): an influential writer, journalist under the Kadar political era in Hungary.

Several years ago, we used to frequently see pages putting unrelated topics on the same page like this because they were known by the same term (see the edit history of tar, which was about computer software and viscous gooey stuff), but I don't recall seeing this odd way of using the word "he" (or "she", or maybe even "it") before. I'd use that word only if referring to the same person.

The page on the mathematician needs something added about notability. Michael Hardy (talk) 18:44, 15 May 2009 (UTC)

I've added some information which I think shows a pass of WP:PROF #1 and likely #3. —David Eppstein (talk) 01:07, 16 May 2009 (UTC)

## Wolfram Alpha and possible use as for reference on mathematics articles

The issue of whether or not Wolfram Alpha can be used for reference on WIkipedia has been raised several other places on WIkipedia. It seems to me that the place is it most likely to be desirable for reference is within WikiProject Mathematics. WIkiProject Mathematics already makes extensive use of Wolfram's other web resources and is familiar with the computational abilities of Mathematica.

So, what guidelines should apply? --Pleasantville (talk) 15:40, 18 May 2009 (UTC)

I do not believe it is a useful source for mathematics articles. The key things we want in a source are additional context and additional depth compared to the Wikipedia article. I looked at Wolfram Alpha briefly, and all it ever gave me was a glorified infobox; less information than a Wikipedia article would provide. — Carl (CBM · talk) 18:23, 18 May 2009 (UTC)

## Fractional part and equation rearrangement

I'm involved with a dispute with an anonymous editor over how to write the fractional part of a number and whether it is permissable or desirable to make some minor rearrangements to an equation rather than copying it directly from a source, and I'd welcome additional opinions on this dispute. See Talk:Calkin–Wilf tree#Newman's formula, and please leave responses there rather than here. —David Eppstein (talk) 16:24, 18 May 2009 (UTC)

## New Featured Article for WPM

A top-priority, frequently-viewed article, Euclidean algorithm, has just been promoted to Featured Article — thanks very much to everyone who helped in that effort!

No article is perfect, so of course I'll continue to (try to) improve this one. I appreciate your keen criticisms and I'll do my best to incorporate them.

I've begun a rudimentary sketch of an article at Fermat's Last Theorem, and I'd be grateful for your suggestions and ideas. If anyone is interested in helping out there, I'd appreciate that as well. The article is still quite primitive, however. Proteins (talk) 05:05, 20 May 2009 (UTC)

## GA Sweeps invitation

This message is being sent to WikiProjects with GAs under their scope. Since August 2007, WikiProject Good Articles has been participating in GA sweeps. The process helps to ensure that articles that have passed a nomination before that date meet the GA criteria. After nearly two years, the running total has just passed the 50% mark. In order to expediate the reviewing, several changes have been made to the process. A new worklist has been created, detailing which articles are left to review. Instead of reviewing by topic, editors can consider picking and choosing whichever articles they are interested in.

We are always looking for new members to assist with reviewing the remaining articles, and since this project has GAs under its scope, it would be beneficial if any of its members could review a few articles (perhaps your project's articles). Your project's members are likely to be more knowledgeable about your topic GAs then an outside reviewer. As a result, reviewing your project's articles would improve the quality of the review in ensuring that the article meets your project's concerns on sourcing, content, and guidelines. However, members can also review any other article in the worklist to ensure it meets the GA criteria.

If any members are interested, please visit the GA sweeps page for further details and instructions in initiating a review. If you'd like to join the process, please add your name to the running total page. In addition, for every member that reviews 100 articles from the worklist or has a significant impact on the process, s/he will get an award when they reach that threshold. With ~1,300 articles left to review, we would appreciate any editors that could contribute in helping to uphold the quality of GAs. If you have any questions about the process, reviewing, or need help with a particular article, please contact me or OhanaUnited and we'll be happy to help. --Happy editing! Nehrams2020 (talkcontrib) 06:23, 20 May 2009 (UTC)

## Allegation of error in a peer reviewed source

Over at Talk:Monty Hall problem/Arguments#Error in Morgan et al? there's a claim that the primary academic source about the Monty Hall problem computes the conditional probability of winning by switching using the wrong Bayesian prior. The source is Morgan, J. P., Chaganty, N. R., Dahiya, R. C., & Doviak, M. J. (1991). "Let's make a deal: The player's dilemma," American Statistician 45: 284-287. Are there any Bayesians here who could comment on this? The specific issue is whether the probability of winning by switching (which is 1/(1+q) where q is the host's preference for the door that has been opened, i.e. door 3 in the usual problem setup) given the noninformative prior should be computed using:

1) a uniform distribution of q in the conditional case, i.e. q is uniformly distributed in the conditional case where the player has picked door 1 and the host has opened door 3. This makes the probability of interest

$\int_0^1 \frac{1}{1+q} dq = ln(2) \approx .693$

or

2) a uniform distribution of q in the unconditional case, so the distribution in the conditional case must be computed as a conditional distribution

$\int_0^1 \frac{1}{1+q} f(q) dq = 2/3$

where f(q) is the conditional distribution of q given the host has opened door 3.

The paper uses #1. Several users are claiming #2 is correct. -- Rick Block (talk) 16:53, 16 May 2009 (UTC)

Note that the in the paper in question, it is clearly the prior distribution of q that is taken to be uniform. They say, '..the noninformative prior in the vos Savan scenario makes this probability...'. Martin Hogbin (talk) 08:38, 20 May 2009 (UTC)

## Ron Larson

We've had a well-written submission at WP:AfC on this person, and would welcome opinions on whether he meets WP:PROF. It can be found at Wikipedia:Articles for creation/Ron Larson (mathematician). Thanks, — Martin (MSGJ · talk) 10:17, 20 May 2009 (UTC)

Having a textbook that goes to nine editions looks like a pass of WP:PROF #4 to me. I don't see the case for the other criteria, but it only takes one. As for the article, it could stand some form of inline citation so we can tell which information which comes from which source, but that's a cleanup issue rather than one of whether it should be kept. —David Eppstein (talk) 16:33, 20 May 2009 (UTC)
The textbook also caught my eye. If there was any doubt, the quality of the article sold me. Most newly-created articles are much less informative and well-written. CRGreathouse (t | c) 19:26, 20 May 2009 (UTC)
There's a fair amount of subjective sentences, verging on peacock, but I agree that it's in a fine state for a new article. It's created; thanks for the comments. — Martin (MSGJ · talk) 20:34, 20 May 2009 (UTC)

The section started by PST was archived due to inactivity, so I am starting another one.

I've moved triadic relation to ternary relation. Michael Hardy (talk) 00:13, 15 May 2009 (UTC)

## Codomain definition

An editor is trying to change the definition of a codomain to say a function is the same if the codomain changes. I believe it is a problem from the way logicians handle functions and then trying to go to the way it is normally done in maths. Anyway discussion at Talk:Codomain#Reverted? Dmcq (talk) 10:15, 23 May 2009 (UTC)

## Efficient arithmetic

Below is my adaptation of something that an anonymous reader added to the article titled complex number recently. user:Paul August deleted it from the article. He's probably right that it doesn't belong in such a prominent place, but it should be somewhere within Wikipedia. Is there a suitable article to insert it into? Then maybe a see-also link from complex number to link there. Michael Hardy (talk) 20:10, 22 May 2009 (UTC)

#### Complex multiplication in only three real multiplications instead of four

In computing the product (a + bi)(c + di), one can reduce calculations in the following way.

Let

\begin{align} k_1 & = c(a+b), \\ k_2 & = a(d-c), \\ k_3 & = b(c+d). \end{align}

Then the real and imaginary parts of (a + bi)(c + di) are as follows:

\begin{align} \text{real part} & = k_1 - k_3, \\ \text{imaginary part} & = k_1 + k_2. \end{align}

This method has been used by computers to reduce the number of multiplications by adding a few additions. This is most commonly used in fast Fourier transforms where one uses only three multiplications and three additions.

#### end of excerpt

Multiplication algorithm I suppose. I guess it might be used in a fixed point integer implementation. The scaling needed for addition with floating point tends to offset any speed gains addition should have compared to multiplication. Dmcq (talk) 20:25, 22 May 2009 (UTC)
In fact it can be useful for the complex multiplication in FFT because the twiddle factors can be precomputed so one only has three adds and three multiplies. So there's a choice between FFT, complex numbers and multiplication algorithms. I'm not sure who discovered it - that would be good for a citation. The article Arithmetic complexity of the discrete Fourier transform gives some amazingly low minimum numbers of multiplies. Dmcq (talk) 12:23, 23 May 2009 (UTC)
I recall hearing that this was discovered by Gauss. But I heard that in a seminar talk, and I don't know a written reference. Ozob (talk) 21:55, 26 May 2009 (UTC)
It would be good to have a reference that this numerical method is used in practice, and is not just a teaching example. At first glance, the method seems susceptible to a loss of precision when ac or bc is large compared to the other terms. Proteins (talk) 16:59, 24 May 2009 (UTC)
These formulas are given as the solution of an exercise in Knuth, although he does not claim they have any practical value and he does include the warning "Beware numerical instability." He doesn't give a reference for this particular formula but does give references for other alternative formulas. See Knuth, Seminumerical Algorithms, 3rd edition (1998), section 4.6.4 exercise 41 (pp. 519, 706). --Uncia (talk) 22:35, 26 May 2009 (UTC)

Added a bit to Multiplication algorithm about it thanks. Dmcq (talk) 22:58, 27 May 2009 (UTC)

## Binomial theorem

I have put a cleanup tag on binomial theorem. It's a typical page about a basic topic which has just grown up in a straggly way: it has duplication, poor structure, an "in popular culture" section, and other indicators of a lack of TLC. Needs a general taking in hand. Charles Matthews (talk) 12:40, 27 May 2009 (UTC)

## Pointer to discussion: Propositional logic or sentential logic?

We currently have an article Propositional logic and a category Category:Sentential logic. I have started a discussion at WT:WikiProject Logic#Propositional logic or sentential logic? --Hans Adler (talk) 13:53, 27 May 2009 (UTC)

## Logarithmic differentiation

Logarithmic differentiation seems to lack good concrete examples, and maybe it's somewhat disorganized. I'll be back.... Michael Hardy (talk) 17:37, 26 May 2009 (UTC)

I would say that log differentiation is used whenever it is easier to differentiate $\ln f(x)$ than the original function, $f(x),$ which is true when
$f(x)=\prod (f_i(x))^{\alpha_i(x)}$
And the function has to be non zero, not positive, because
$\frac{d}{dx}\ln |x|=\frac{1}{x}$
(Igny (talk) 23:26, 26 May 2009 (UTC))
@MH: shortly after the origination of this article, some complained about it being too textbook-like because of the examples it incorporated. They were therefore removed and taken to Wikibooks. —Anonymous DissidentTalk 02:34, 30 May 2009 (UTC)

## Unrendered TeX

For several hours now, when I save a page or preview a page, some of the lines of TeX fail to get rendered. Wikipedia usually works well in that regard, but not today. Have others had that experience? Michael Hardy (talk) 19:40, 26 May 2009 (UTC)

Do you mean they just render as normal HTML but not image? You can change that in your preferences. --Visit me at Ftbhrygvn (Talk|Contribs|Log|Userboxes) 01:50, 29 May 2009 (UTC)

No—I meant I just saw the TeX code.

It hasn't happened today, though. Michael Hardy (talk) 01:57, 29 May 2009 (UTC)

I saw it few times in the past few days. It went away after few seconds by itself, or on page reload. Jmath666 (talk) 04:56, 29 May 2009 (UTC)
I've seen it before. The reason you see the TeX code is that the browser (Firefox?) shows the alt-text of an image when it fails to load. Shreevatsa (talk) 12:58, 29 May 2009 (UTC)

## Surface area

This article is currently shocking. I'd write it myself, but do need feel comfortable in my ability to be rigorous enough. Any help would be fantastic. —Anonymous DissidentTalk 02:31, 30 May 2009 (UTC)

OMG! The rating is completely wrong! It should be a top-priority stub! It MUST be improved! Unfortunately, I am currently busy for my exam and improvement works on Matrix. I will start working on this when I have more spare time. Visit me at Ftbhrygvn (Talk|Contribs|Log|Userboxes) 03:47, 30 May 2009 (UTC)
Looking through the history, there used to be a lot more to this article. For some reason it was pared down to a bare four sentences. I'm not really sure why. —Bkell (talk) 04:10, 30 May 2009 (UTC)

I have restored the seemingly last complete version, I had to go more than a year back for that. This article gets shocking amounts of juvenile vandalism, in addition to some unscrupulous edits and edits whose motivation escapes me as well. I suspect the reasons for vandal's attention are similar to the situation at Geometry. Given its history and difficulty of maintaining an article under such circumstances, I propose to semiprotect it indefinitely. Arcfrk (talk) 06:11, 30 May 2009 (UTC)

User:TedPavlic seems to be intent on changing "References" sections into "Further reading". This seems quite unwarranted. As far as I know, there is no rule that References sections must contain only footnotes. Indeed, most mathematics articles on Wikipedia seem to do just fine without an enormous proliferation of footnotes. I'm going to be undoing most of these changes, unless there are significant objections here. Sławomir Biały (talk) 19:42, 30 May 2009 (UTC)

Fair enough but I couldn't see anywhere on his Talk page where you've told him you disagree with what he is doing. Have I missed something or were you just coming here to see what other people thought first? Dmcq (talk) 20:48, 30 May 2009 (UTC)
I have posted a message on the user's talk page, per your recommendation. My reason in posting here first is that it seems to me that editorial decisions like this that potentially effect a great number of articles should be made in the open rather than in users' talk pages. Sławomir Biały (talk) 22:29, 30 May 2009 (UTC)

## Zero element or zero elements or.....?

What shall we do with this situation? Michael Hardy (talk) 04:56, 31 May 2009 (UTC)

I believe the parenthetical there would make the change correct.Julzes (talk) 05:12, 31 May 2009 (UTC)
OOPS. Hold on the parenthetical should be removed from the original!Julzes (talk) 05:14, 31 May 2009 (UTC)
I didn't manage to find the phrase "semigroup with zero element(s)" in the Grillet reference, so I'm not convinced this isn't a neologism, in which case its probably just poor grammar. I suggest changing it to "Empty semigroup" or "Semigroup with no elements" unless it can be shown that "semigroup with zero element(s)" is actually a way it is referred to. RobHar (talk) 05:18, 31 May 2009 (UTC)
Yes (e/c), that's something like what I was trying to say. It seems that the old definition of semigroup is being brought in line with category theory type thinking.Julzes (talk) 05:23, 31 May 2009 (UTC)
And, furthermore, I would check whether a categorical framework might not be common modern practice for the possibility of improving the semigroup and perhaps other articles.Julzes (talk) 05:33, 31 May 2009 (UTC)
I WP:BOLDly moved it to empty semigroup. "With zero elements" is not typical English usage (it would more idiomatically be "with no elements" or "without any elements") and the "zero element" phrasing made it too easily confused with a monoid (a semigroup that, using additive notation, has an element that acts like the number zero). I haven't done anything about the contents, though. —David Eppstein (talk) 07:32, 31 May 2009 (UTC)
That seems like a good way to start, but the whole category theory approach might find a regular place in the algebra articles generally.Julzes (talk) 07:35, 31 May 2009 (UTC)
The group (mathematics) article is a good case in point. It looks like a beautiful article, but mentioning categories might be a good thing in the introduction, say after mention that groups are a kind of algebraic structure.Julzes (talk) 07:42, 31 May 2009 (UTC)

Should Semigroup with one element also move to Trivial semigroup? —Dominus (talk) 21:25, 31 May 2009 (UTC)

Yes, that seems better.Julzes (talk) 02:14, 1 June 2009 (UTC)

## PR

I have requested a PR for Matrix. Please comment on the article so that I can improve it to FA. Visit me at Ftbhrygvn (Talk|Contribs|Log|Userboxes) 13:05, 31 May 2009 (UTC)