I agree. I wouldn’t consider someone who has taken (and remembers) a course in set theory a beginner without some added qualifier.

One of my pet peeves is using mathematical symbols beyond basic arithmetic without introducing them once by name. Trying to figure out what a symbol is and what branch of math it comes from is extremely frustrating.

I haven't taken any courses in set theory, but it makes perfect sense to me. Once someone tells you that the funny script 'R' means "Real numbers", the funny E means "is an element of", and the vertical | means "given that," that's pretty much all you need to know to dive in.

If those concepts cause difficulty, it probably makes sense to go back down the learning curve a bit before tackling linear algebra. Alternatively, just cut and paste the expression into any LLM and it'll explain what's what.

VLLMs are incredibly good at decoding math from screenshots, if you’re working from a PDF textbook. ChatGPT especially, and since it’s conversant in LaTeX, it can respond directly in the notation you don’t recognize to break it down for you. It even manages with photos of my handwritten scrawl (mostly).

There are a handful of textbooks that have a nice appendix that defines each symbol (or maybe sometimes tells you where you can go to learn more about the topic represented by the symbol!). That way they can presume that most readers are already familiar but still be helpful to those who aren't.