Improve legibility of formula from developer guide

[MarcoGorelli]

This formula in the developer guide doesn't look great

I think it should be possible to write it with LaTex?

Am opening this as a good first issue, but I'll take it if nobody does. New contributors welcome!

[CloudChaoszero]

Hey @MarcoGorelli! Hope you had a good holiday.

I am happy to submit a PR for this, and other LATEX-related formula inconsistencies on this page.

[MarcoGorelli]

awesome, thanks!