Over at John Cook’s TeX Tips there’s a pointer to a very nice MathJax
basic tutorial and quick reference. It’s especially handy for those
who don’t use all the time but occasionally want to
include a bit of mathematics in a blog post. It by no means covers
everything but there’s enough there to probably get you through adding
a quick formula or two to a post.
The very first tip is something that I didn’t know. When you’re
looking at a Web site with some MathJax generated mathematics can you
can see the source by right clicking on the formula
Show Math As →
TeX Commands. That will open another
tab with the source.
The cheat sheet is definitely worth bookmarking if you’re not a
expert but sometimes want to include some
mathematics in a post.
Postscript: After writing this, I came across this macOS application
that lets you take a screenshot of an equation and output the LaTeX
source. If the tip about right clicking on a MathJax-displayed
equation to display the appeals to you, you should
check out Mathpix.