Important machine learning equations

While this very much looks like AI slop, it does remind me of a wonderful little book (which has many more equations): Formulas Useful for Linear Regression Analysis and Related Matrix Theory - It's Only Formulas But We Like Them [0]

That book is pretty much what it says on the cover, but can be useful as a reference given it's pretty thorough coverage. Though, in all honesty, I mostly purchased it due to the outrageous title.

0. https://link.springer.com/book/10.1007/978-3-642-32931-9