Right-clicking on a piece of latex code brings up a MathJax context menu that includes useful items like
Show Math As > (choose between mathml and Latex commands); and
MathJax Help.

Right-Clicking on the first piece of code above (which is MathJax Latex) gives that, whereas doing it on the second, which is Unicode, does not.

There is a good $\LaTeX$ primer on physicsforums here.

MathJax is a Java implementation of LaTeX that interacts with the web browser.Stand-alone LaTeX uses $ and the double-dollar-sign as delimiters for in-line and separate line ('display style') formulas. MathJax implementations usually don't recognise those because that would prevent people from using the $ sign outside of equations.

physicsforums uses ## as delimiter for in-line but keeps the double dollar sign for display style since one doesn't normally type a double dollar sign in ordinary text.

As Srap discovered above, the in-line delimiters for this forum are [ math] and [ /math] but without the spaces inside the square brackets (which I inserted here to stop MathJax from interpreting them as delimiters - a classic 'use' vs 'reference' distinction that language philosophers will enjoy).

I don't know what the delimiters are for display math. I tried a few of the usual things like \[, $$ and [tex] but they didn't work. The forum maintainers would know.

• MathJax basic tutorial and quick reference (2016)
• LATEX Tutorials A PRIMER (2003)
• Getting Started with LaTeX (1995) » Mathematical Symbols


Note, the forums do not support MathJax completely; there are some limitations here and there (e.g. multiple lines of LATEX).


The Basel problem:

$\sum_{n=1}^\infty \frac{1}{n^2} = \frac{\pi^2}{6}$



Function continuity:

$f$ is continuous at $d$

$\forall \epsilon \in \mathbb{R}_{+} \Bigl[ \exists \delta \in \mathbb{R}_{+} \bigl[ \left| x - d \right| \lt \delta \Rightarrow \left| f(x) - f(d) \right| \lt \epsilon \bigr] \Bigr]$



... and God said ...

$\begin{aligned} \nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} & = \frac{4\pi}{c}\vec{\mathbf{j}} \\ \nabla \cdot \vec{\mathbf{E}} & = 4 \pi \rho \\ \nabla \times \vec{\mathbf{E}}\, +\, \frac1c\, \frac{\partial\vec{\mathbf{B}}}{\partial t} & = \vec{\mathbf{0}} \\ \nabla \cdot \vec{\mathbf{B}} & = 0 \end{aligned}$


... and there was light.

Thanks guys!

Despite some limitations, should be good enough for our proposes.

Based on Jorndoe's post, it appears one can get displaystyle by using the same delimiters .
and then using the standard latex delimiters for display style inside there, eg
$\begin{align}\sum_{i=1}^n r^2 = r\ \frac{1-r^{n}}{1-r}\end{align}$
which used the code

We can tell that it's display style because the subscripts and superscripts for the sum are directly above and below the $\Sigma$, instead of to the right of it.

One thing about MathJax though is that its functioning varies between browsers. My post above looked fine to me when I did it at home this morning on Firefox on Linux, but now, at work on IE in Windows, it interpreted some of the double-dollars as delimiters and made a whole bunch of ordinary text into unreadable pseudo-math. I have fixed that up now so it looks proper on IE-Windows, but I wonder what it will look like from my home computer.