Someone training as a data scientist asked me for help typesetting in LaTex. I had less experience of it than she did, but being familiar with hypertext mark-up allowed me to pick up LaTex pretty quickly.

LaTex pre-dates modern mark-up languages so it isn't the most elegant language but it is the de-facto standard for typesetting mathematical and scientific papers. It can typeset extremely complex formulae, which HTML cannot do yet.

Wikipedia has partly integrated LaTex. Formulae are typeset by LaTex and converted to images, which are then embedded in Wikipedia HTML pages.