Guidelines for good use of MathJax in question titles

Question

Motivation:

Every once in a while, I find myself making edits like this one, where OP (likely due to inexperience in asking questions) has used display math mode ($$ delimiters) and/or the \displaystyle or \dfrac commands in ways discouraged by the community.

This issue has been around for a while, see e.g. this meta question.

In line with the more-or-less universally supported initiative to be more communicative to especially new users, I have been making remarks similar to the one I just added to the comment templates thread, giving a short explanation of why not to use these functionalities of MathJax in titles.

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Question:

In an attempt to make this all more accessible to new users without them having to commit one of these mistakes, this question intends to gather all guidelines on the use of MathJax in question titles in one place, the CW answer to this question.

Answer 1

In addition to the below title-specific $\rm\LaTeX$ guidelines, there is of course the MathJax tutorial and quick reference.

1. The primary rule for using $\rm\LaTeX$ in titles is to be vertically terse. Try to make your title take up as little vertical space as possible (the height of $\sum\limits_{n=1}^\infty$ is an approximate upper bound for what is admissible). In particular:

   • Do not use display math mode ($$ delimiters) or \displaystyle to force big integrals, sums, and other constructs. Similarly, avoid constructs like \dfrac or \dbinom which implicitly use display mode. To achieve $\lim\limits_{n\to\infty}$, the \limits command exists: \lim\limits_{n\to\infty};

   • Do not use \left and \right (or other scaling commands) when this yields very large brackets. Furthermore, do not use environments in titles (such as the "cases" environment \begin{cases} .. \end{cases}).

   What is the rationale behind these rules for limiting vertical space?

   The main page contains the recent questions. Its vertical space is very limited, and therefore valuable. Using big $\rm\LaTeX$ in your title will push other questions outside of the visibility range of (some) visitors; because one question is not inherently better than another for using such constructs, they are to be avoided at all times.

2. Ensure that the title contains some actual words, and not only $\rm\LaTeX$ -- the search functionality of MSE does not interact well with typeset mathematics, making questions comprising only $\rm\LaTeX$ (much) harder to find. Furthermore, the MathJax context menu (which pops up when you right-click on some typeset expression) overrides the browser's link context menu, making e.g. opening the question in a new tab difficult.

3. Do not use MathJax to typeset (e.g., italicize) your title. It does not look nice in plaintext fields like users' notifications, and questions with MathJax in their titles will not be shown in the "Hot Network Questions" list.

Answer 2

Currently, questions with TeX markup in title are excluded from Hot Network Questions. On one hand, this removes the concern about users of other SE sites seeing unparsed markup in the sidebar. On the other hand, this raises the concern about users of other SE missing out on accessible Math.SE posts they would be interested in. I think this aspect should be considered when editing questions that can be useful to a broader audience, especially when the benefit of markup is purely cosmetic.

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Concrete example: an experienced user slightly edited a question title from

can someone explain how tanx/secx = sinx?

to

Can someone explain how tan x / sec x = sin x?

but refrained from introducing TeX markup. This allowed the question to stay in Hot Questions and amass 1300+ views in less than one day. But when another user edited the title to

Can someone explain how $\frac{\tan x}{\sec x}=\sin x$

that was the end of the question's popularity: it was immediately removed from the sidebars around the network.

Answer 3

Markdown doesn't work in titles, so occasionally people will use MathJax as an approximation.

$quod\;erat\;demonstrandum$                   produces     $quod\;erat\;demonstrandum$

Please don't do this; honestly, trivial formatting is not necessary in a question title (and it doesn't look nice in the "hot questions" list, which does not render MathJax). You'll have the opportunity to do all sorts of fancy formatting in the question body. If you simply can't live without your title having formatting, do it right.

$\textit{quod erat demonstrandum}$     produces     $\textit{quod erat demonstrandum}$

There's a difference. From this page:

When writing equations, LaTeX assumes that a series of letters without spaces represents a set of distinct variables and typesets them accordingly: with an extra bit of space between each of them, in order to emphasize that they are distinct entities. Therefore, if you want an actual word, use \mathit (math italics) or \mathrm (math roman): $x_\mathit{max}$, not $x_{max}$...

Similarly, $text$ is not the approved way to write italics in regular body text (for the same reason as above)...

Besides making spacing between the letters correct for text, and making the \; spaces unnecessary, the \textit command is semantically correct in my example, since the italic font is being applied to something non-mathematical.

Answer 4

I think that we should also forbid \newcommand on the title. Sure, if done right there's no harm in this, but this can be a huge slippery slope for either small mistakes that accumulate to ravage the front page, or worse.