Wikipedia talk:Manual of Style/Mathematics

Angle brackets

Is there a preference with respect to the usage of "proper" Unicode angle brackets versus "faking" them with less than/greater than signs? Apparently, the angle brackets in an expression like 〈v,w〉 (using &lang; and &rang;) are not displayed properly for many users. Should one write this expression as <v,w> instead? —Tobias Bergemann (talk) 08:50, 10 June 2009 (UTC)

The proper use are the r/l angles. If they don't display correctly, these won't be the only things to not display correctly. This isn't the internet of 1995, and any modern browser uses default fonts which supports them.Headbomb {^ταλκ_{κοντριβς} – WP Physics} 06:49, 25 June 2009 (UTC)

Italicization of π / Pi

The Greek letter pi is italicized in some parts of the Pi article, and roman in others. That needs to be fixed, but which is correct?

67.171.43.170 (talk) 02:37, 17 September 2008 (UTC)

Pi should be italicized; π should not be. Septentrionalis PMAnderson 16:58, 20 September 2008 (UTC)

Not exactly consensus, but I agree and boldly made the change throughout (in celebration of this glorious day), but e still appears italicized. Note that, as a constant, this is different from the several variables that appear italicized (d, r, etc.), although I'm not 100% sure what's proper there, either. Out of curiosity, would $\pi$ be an option for the article body? Or $e$? /Ninly (talk) 16:04, 14 March 2009 (UTC)

WRONG. π should always be italic, for the following reasons..

1. The tradition of mathematical typography is to italicize π. There is discussion of whether this is 'correct' but the lower-case italic form $\pi$ is the most widespread in the literature. (π is italic when it denotes the standard meaning of pi in trigonometry, calculus, physics, etc -- but deviant statisticians use π and Π to symbolize other stuff).
2. MathML, LaTeX, and Wikipedia tags {{math}} or <math> all italicize $\pi$.
3. From Edward Tufte's website:
“ These traditions are hundreds of years old. Italics help distinguish between variables and other things like numbers and operators. For instance cosine of x is written "cos $x\,\!$". (This issue comes up in other symbolic systems; programmers need that distinction too, but today almost universally use color coding instead.) But like any centuries-old tradition, there are a lot of quirks, for example vector variables are sometimes bold, non-italic. Also which letters you use for which variables is important. A lot of today's traditions were introduced by Descartes, like using the end of the alphabet for unknowns and the beginning for known quantities. At one point people used vowels vs. consonants, I think, but no longer. ”
4. According to Stephen Wolfram:
“ One of the things that Euler did that is quite famous is to popularize the letter $\pi$ for pi--a notation that had originally been suggested by a character called William Jones, who thought of it as a shorthand for the word perimeter. ”
5. Most fonts are non-mathematical and render &pi; as "π" (non-italic). But mathematical typesetting packages render \pi as "$\pi \,\!$" (italic).
6. The Pi article even shows this italic image of the letter! ---

I believe this article should follow mathematical convention, so I would prefer to italicize the π's. Any objections? ~~ Ropata (talk) 05:38, 17 June 2009 (UTC)

The Wikipedia Manual of Style clearly asks not to italicize π (or any other Greek letters for that matter, except possibly when they are variables). The discussion really belongs to WT:MSM, not here. — Emil J. 11:54, 17 June 2009 (UTC)

The discussion is already here, not at WT:MSM. The Manual of Style does not enforce rules, it merely states a few conventions. Wikipedia ought to follow mathematical convention not reinvent it. ~~ Ropata (talk) 11:00, 20 June 2009 (UTC)

That the discussion already started here does not make the choice any more appropriate. People who are interested in conventions for formatting Greek math symbols are supposed to watch the MoS page, they are not supposed to watch every article which uses the symbols such as this one. — Emil J. 14:25, 23 June 2009 (UTC)

My understanding is that italicizing Greek is redundant because Greek letters are already somewhat slanted (or at least their supposed be even though some computer fonts don't show them that way. For another project Angr wrote:

The Greek alphabet doesn't distinguish between italic and roman types; Greek letters themselves are usually printed slightly inclined to the right, especially in fonts used for Ancient Greek rather than Modern Greek. (Modern Greek fonts are often assimilated to the Latin alphabet, having completely vertical lines and distinguishing between serif and sans-serif fonts.) At any rate, even though the Greek will look slightly italicized to people used to the Latin alphabet, it shouldn't be set as italics.

--RDBury (talk) 05:37, 25 June 2009 (UTC)

Good advice

can be found at http://www.maths.ox.ac.uk/files/study-guide/index.shtml, esp. part II. I found this info out far too late to be of any use to me, but I felt good knowing that someone made explicit the process of writing theorems (or I was away at the lecture they told everyone else)...

Perhaps this should be basic knowledge for anyone actually writing a maths article on WP. Otherwise a link to it may be helpful. 118.90.74.32 (talk) 02:22, 16 July 2009 (UTC)

Inline math notation

(moved from Talk:Torque)

So, apparently inline LaTeX is discouraged, but not prohibited. From the guidelines it is seen that you still can use LaTeX without getting the full size PNG, which keeps the height of the line almost the same as when using text. For example, $\tau$ is obtained using LaTeX but it is not as big as $\tau \,\!$. I think both symbols are better than using the text symbol τ, which is nowhere close to the symbol $\tau \,\!$ from the equation. So, I am asking for people's opinion on this matter. How do you want the article to look like: with inline equations using text or LaTeX? sanpaz (talk) 04:06, 17 July 2009 (UTC)

In a perfect world I'd like to see <math></math> used for everything, but as things currently are, LaTeX PNGs stick out from the rest of the text like a sore thumb. (Too bad the MathML option on Wikipedia is so wimpy—just about the only time it seems to kick in is with simple fractions.) Getting consistency in appearance between the text and the out-of-line equations is definitely a problem, and I can definitely see why so many editors prefer inline PNG rendering. Strad (talk) 18:30, 17 July 2009 (UTC)

Is there some reason you bolded the tau in your text symbol example? Either the regular τ or the italic τ looks better, I think. On my browser, all your TeX-formatted examples are significantly larger than the size of the text. My opinion: text wiki formatting of math is ugly but mis-sized inline bitmap images are even uglier. So I prefer the wiki formatting. —David Eppstein (talk) 00:15, 18 July 2009 (UTC)

I don't think this should be anything individual editors have to worry about. Ideally, editors would simply tell the software that some text is is mathematical, and then the software would display it appropriately. Having editors use different markups just to circumvent the limitations of the software is just a hack. If this view is shared by a majority, then I could enter an enhancement request at bugzilla. (There seems to be none yet ; see https://bugzilla.wikimedia.org/buglist.cgi?query_format=specific&order=relevance+desc&bug_status=__open__&product=MediaWiki&content=math.) — Sebastian 00:21, 18 July 2009 (UTC)

Would you propose to fix this by instituting the mis-sized bitmaps whenever any text is called out as mathematical, or by restricting mathematical formulae to the limited options available in wikiformatting? Neither is satisfactory for all purposes, and until all browsers support MathML they're what we're stuck with. —David Eppstein (talk) 01:02, 18 July 2009 (UTC)

To be honest, I don't know enough about the technical implementation, and maybe I'm misunderstanding something here. What I'm getting out of the conversation so far is that we have two basic ways to enter simple mathematical text: (1) without markup, as in "τ"; (2) with markup, as in <math>\tau</math>. (Each of these can be modified, e.g. by bolding it or by adding "\,\!", but I'm glossing over these subtleties here.)

I only thought about it at the level of how we enter the text. My proposal is on this higher level, not about a specific bug fix. (This is why I think of it as an enhancement.)

Now, let's assume that we have sufficient consensus that the bitmaps are uglier than the inline text. So far, we have been trying to address this through the MOS, by discouraging inline math markup. But if we have that consensus, then there is no reason to even offer the choice. The enhancement I propose would shift that worry onto the software, so that editors only need to decide whether a text is mathematical or not. If an (inline) math text can be displayed as plain text, then the software will do so. If not, it will display as a bitmap. I think this is a more elegant and logical solution. — Sebastian 02:16, 18 July 2009 (UTC)

Besides text and math markup, you can also use html tags which is what the x² and x₂ buttons above the editor window generate. Theoretically, you could also type in the MathML directly as well, but there are a lot of browsers that still don't support it (as mentioned above). In my experience there is no good solution, at least the way things stand. For example, what do you do with something like ${\vec {v}}$? It's impossible (or at least very difficult) to do without math markup but putting a single character in it's own line seems silly. What I try to do to carry on with the established style in the article, even if I disagree with it, on the theory that eventually the situation will improve and it's not worth tweaking formulas until then.--RDBury (talk) 06:11, 18 July 2009 (UTC)

Just some background info: As I understand it (correct me if I'm wrong) the way the server handles math markup is to first try to convert it to either html or MathML, depending on the user's preference settings. Only when the formula is too complicated, which it usually is, is it converted to PNG. In an ideal world, the server would be able to convert any LATEX code to MathML code, but the conversion program to do that is still under development. So the math markup is usually converted to PNG, and that conversion is done by an open source program developed externally. The problem with that program is that it doesn't know what font you're using in your browser so it picks a size that it thinks is reasonably legible. You can see this by bumping up the font size in your browser; all the text gets bigger but the math that gets converted to PNG stays the same size. In fact, you could "fix" the size mismatch problem by fiddling with the font settings in you browser, but then you've got huge text and there are still alignment problems.--RDBury (talk) 06:41, 18 July 2009 (UTC)

Imaginary unit

Some articles (such as Z-transform) needlessly use j instead of i for imaginary unit, which can confuse readers. Can there be any addition in this Manual of Style (or maybe somewhere else) that will encourage the usage of i as imaginary unit? --93.136.201.179 (talk) 13:31, 19 July 2009 (UTC)

That's common in electronics and by extension signal transforms because i might stand for current. Dmcq (talk) 13:40, 19 July 2009 (UTC)

Articles in question don't use electrical currents in their formulas and certainly don't use lowercase i for electrical current, so there is no need to confuse readers by usage of j for imaginary unit in those articles.

Also, electric current is usually written as uppercase I. --93.136.201.179 (talk) 14:03, 19 July 2009 (UTC)

Perhaps the articles don't mention electrical currents, but if I'm not mistaken, the Z-transform is frequently used in electrical engineering. Certainly an article using j for the imaginary unit should say that that's what that notation means. Michael Hardy (talk) 15:25, 19 July 2009 (UTC)

See Wien bridge for a simple example of i and j occurring together. In fact there they have i_in, i_out but people also say I and i to distinguish them. The usual rule in wikipedia for things like this is the first person to write a article sets the style. Dmcq (talk) 16:11, 19 July 2009 (UTC)

Also, it's inappropriate to force one convention across all of Wikipedia when several conventions occur in practice (just as in American vs. British spelling). As long as each article makes clear what i and j stand for, then we're doing as well as we can. Ozob (talk) 21:28, 20 July 2009 (UTC)

Fully agree. Both mathematicians as well as electrical engineers should know these formulae anyway and can figure out what j stands for in this context--Tprosser (talk) 11:18, 21 July 2009 (UTC)