# Wikipedia talk:Manual of Style/Mathematics

WikiProject Manual of Style
This page falls within the scope of WikiProject Manual of Style, a drive to identify and address contradictions and redundancies, improve language, and coordinate the pages that form the MoS guidelines.

## Use of mathematical notation in non-math articles

I have edited the first sentence to say that some aspects of this manual apply not only to articles on mathematics but also to the use of mathematical notation in articles on other subjects than mathematics. It would be absurd to say that because an article using mathematiacl notation is on chemistry, it should be exempt from standard conventions when it uses mathematical notation.

The article titled Duckworth–Lewis method begins by saying:

The Duckworth–Lewis method (often written as D/L method) is a mathematical formulation designed to calculate the target score for the team batting second in a limited overs cricket match interrupted by weather or other circumstances.

But someone is saying on its talk page that WP:MOS does not apply to it since it is not a mathematics article, so that one should write things like 3<5 instead of 3 < 5 or 3 x 5 instead of 3 × 5, etc. Michael Hardy (talk) 12:06, 5 May 2014 (UTC)

## phi problems

There are two different ways to include the phi symbol:

a wrong φ  ampersant phi semicollumn


and

a right  $\phi$ math phi math


and in some articles they both appear for example in Angle of parallelism is it not possible to make a script that automaticly change the wrong form into the right form? (for beginners it can be unclear that they have the same meaning)

Bad idea I think. I've seen both variants of epsilon used together for different things. They are just math symbols, we are not writing Greek. They are not right or wrong. Dmcq (talk) 12:28, 13 July 2014 (UTC)
You can also get the "open" phi with varphi in math mode, i.e. $\varphi$. I think it is the preferred choice for e.g. the golden ratio. I see no point in prohibiting it or the other one. —David Eppstein (talk) 14:16, 13 July 2014 (UTC)
Consistency within an article is good, but is there a way of ensuring that across all combinations of HTML rendering and LaTeX rendering? Deltahedron (talk) 16:38, 13 July 2014 (UTC)

## Variable re-use

Do we need an admonishment to avoid using the same variable name for multiple unrelated meanings? This has come up in Closed subgroup theorem. (There doesn't seem to be any disagreement there that this is a bad idea, but it happened because one contributor was following the style of a reference that did this.) —David Eppstein (talk) 16:49, 18 July 2014 (UTC)

Recommending against variable reuse is a good idea. It should come up only rarely, but the advice is certainly in keeping with the general principle of providing maximum clarity in an article. Something like
• Avoid using the same variable or symbol for two different mathematical objects.
--Mark viking (talk) 17:48, 18 July 2014 (UTC)
I think some qualifier such as "where confusion is likely to arise" is needed. There are quite standard ways of writing which would be excluded by this if rigorously enforced. For example, if (X,T) is a topological space with underlying set X and topology T, it is quite usual to refer to it as X if there is only ever going to be one topology on it. Similarly we use +, ×, ⋅ etc to denote operations in different groups freely without confusion. The reuse of place-holders such as i,j for summation is also usual. Deltahedron (talk) 08:29, 19 July 2014 (UTC)

## Blackboard Bold Unicode

"A particular concern for the use of blackboard bold on Wikipedia is that these symbols must be rendered as images because the Unicode symbols for blackboard bold characters are not supported by all systems."

Is this still true? --Unverbluemt (talk) 11:27, 31 August 2014 (UTC)

According to [1], in July, Wikimedia sites collectively got over a billion requests from IE 7 and below; plus hundreds of millions of requests from very old versions of Chrome and Firefox. I think that while Unicode blackboard bold is not as problematic as it once was, in the interest of maintaining wide compatibility it is still best to avoid it. Ozob (talk) 16:38, 31 August 2014 (UTC)