A reader at the Math 3 level can read the sorts of things that a research-level mathematician could — if you’re Math 3, it’s okay to throw LaTeX formulas straight at you, using standard notation, with a minimum of handholding.
At the Math 3 level, different schools of mathematics may have their own standard notation, so somebody who is Math 3 in one discipline or subject may not necessarily be Math 3 in another.
Writing for a Math 3 audience
When writing for a Math 3 audience, all bets are off on readability. You can use as much formal notation as you like in order to define your point properly and clearly.