New video out on eqn, which is a groff/troff preprocessor that automatically formats mathematical expressions. It can be compared to LaTeX's math mode, but I actually enjoy the syntax much more.
In the vid, we go from basic math to square roots, summation, integrals, defining
eqn macros and doing inline code.
You can get more info on the kinds of things you can get done with
eqn with the cornucopia of documentation here: https://troff.org/papers.html#eqn.