An evergreen post
Testing
January 20, 2021
Rendering mathematical equations
Examples from the 
mathjax demo.
But they work with katex as well.
Rmarkdown
In .Rmarkdown documents, you can use either
$a \ne 0$
to get inline math: \(a \ne 0\).
There is no conflict with using dollar symbols regularly, because knitr automatically escapes freestanding dollar symbols.
And you can use
$x = {-b \pm \sqrt{b^2-4ac} \over 2a}.$$
to get a math paragraph:
$$x = {-b \pm \sqrt{b^2-4ac} \over 2a}.$$
md
In .md documents, you can not use the single dollar syntax.
The double dollar syntax still gives you a math paragraph.
$$x = {-b \pm \sqrt{b^2-4ac} \over 2a}.$$
$$x = {-b \pm \sqrt{b^2-4ac} \over 2a}$$
In order to get inline equations, use:
`\(a \ne 0\)`
or
\\(a \ne 0\\)
to get: \(a \ne 0\).