Wikipedia talk:WikiProject Mathematics

Links to discussions

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

• Talk:Triadic relation#Article rewritten; proposed move to ternary relation over redirect --Hans Adler (talk) 23:09, 14 May 2009 (UTC)
• Talk:Relation (mathematics)#Merge directed relation – Relation (mathematics) is a strange tiny content fork of finitary relation/binary relation. What do we do with it? --Hans Adler (talk) 23:42, 14 May 2009 (UTC)
• Talk:Order theory#GA Reassessment - Several important points were made by User:Geometry guy here, but to no avail. --PST 09:17, 24 May 2009 (UTC)

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

${\begin{aligned}k_{1}&=c(a+b),\\k_{2}&=a(d-c),\\k_{3}&=b(c+d).\end{aligned}}$

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

${\begin{aligned}{\text{real part}}&=k_{1}-k_{3},\\{\text{imaginary part}}&=k_{1}+k_{2}.\end{aligned}}$

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)

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)

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 Dissident^Talk 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)

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)

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 Dissident^Talk 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)

References to Non-Newtonian calculus

References to Non-Newtonian calculus are being added to to the 'See also' section of various articles related to the exponential function. They don't seem relevant enough to warrant inclusion, but what should I put into a comment when removing them - is there a guideline please? Or do you think they are reasonable? Dmcq (talk) 16:01, 30 May 2009 (UTC)

The guideline is WP:SEEALSO, although it leaves it mostly up to the judgment of the editor. "See also" is slightly deprecated, in the sense that it is better to weave the items into the narrative. My opinion is that this subject is irrelevant to the exponential function, so I would be bold and delete the links with the comment "remove irrelevant wikilink". --Uncia (talk) 16:36, 30 May 2009 (UTC)

References -> Further reading crusade

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)

Looking for help with mathematical coincidence

There is current and threatened editorial action on the article mentioned. The article is primarily a list, and I would like to improve its nature. I would also categorize it as a part of mathematics education, if such is possible. I have one citation to "attempted" work by a CalTech Ph.D. at zhurnaly.com/cgi-bin/wiki/CoincidentalTaxonomy that I would like to use or suggest as being used in the article. I also think the article might be re-directed to a larger article on mathematical curiosities. I have my own original results that I deem not to be research that I also would like to place in the introduction or body of the article as well. This is the subject matter you can find at User:Julzes/365.25. The results were found by happenstance, this being my explanation for not regarding them as research, and I have no interest in staking a claim to them.Julzes (talk) 04:40, 31 May 2009 (UTC)

Somebody's (or several somebodies) have been having a lot of OR fun. I wouldn't be displeased if it was just deleted. --C S (talk) 06:05, 31 May 2009 (UTC)

Well, I can understand that point of view from someone interested in 4-dimensional topology, but you have to acknowledge that users of lower levels might benefit if such an article were really well-written rather than in its current pathetic state.Julzes (talk) 06:44, 31 May 2009 (UTC)

I have no idea what you are going on about. The article is in violation of Wikipedia policies, which is why you've been getting different people commenting likewise on the talk page. You haven't been around for too long, so you should consider that you aren't really understanding what's viable content or not. In particular, I recommend thoroughly reading and digesting WP:OR. And I mean, really trying to understand it, not trying to parse it in a way that justifies your article -- that's a mistake a lot of newcomers make, and not surprisingly, they always parse the policies in a way that justifies their articles that a lot of experienced Wikipedians who have long familiarity with policies don't agree with. --C S (talk) 06:54, 31 May 2009 (UTC)

I've been down this road, and I'm trying to get the exception on routine calculations clarified. You're no help, and it's not "my" article.Julzes (talk) 07:06, 31 May 2009 (UTC)

Thanks for pointing out the article. I'll have a quick search with google books if any of the 'fact' ones strike me as interesting but otherwise Wikipedia can't be used as a repository for odd bit of numerology people dream up, it has got to satisfy notability. If nobody can find citations then they should be removed. Dmcq (talk) 07:48, 31 May 2009 (UTC)

Don't rush it, though, if that's your attitude. BKell set a two-week deadline a few days ago.Julzes (talk) 10:45, 31 May 2009 (UTC)

By the way, in the current article the fact that the square root of 2 plus the square root of 3 is a fair approximation to pi has been arbitrarily removed ahead of schedule (along with one that is more precise but also more complex), and the article does not even contain the coincidence involving simply e and its base-ten representation or that of the common logarithm of 2. All these things should be in a wikipedia article somewhere, and if not this article then where? Finding sources for notability's sake should not be top priority. Fixing things like this should.Julzes (talk) 10:53, 31 May 2009 (UTC)

Not all things should be in Wikipedia. It is not an attempt at forming The Library of Babel. Notability is a basic requirement. There's places and in Wikipedia to discuss changing basic things like this but |I don't think you'll get far with this one. Dmcq (talk) 12:17, 31 May 2009 (UTC)

Some things are a kind of mathematical common knowledge. Consider if instead of the article in question saying that log₁₀2= 0.30103 it were corrected to show how close it is to this.Julzes (talk) 12:48, 31 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)

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)