Or... Hear me out... Don't take notes at all. I'm sure I can find supporting material that is just much better than my paltry notes. I find that for me, it detracts from engaging with the material. I just much better prefer to listen and engage and think what is being said.

I only take notes if I am trying to work out some of the things said or as support for this or that or maybe 2 really interesting lines or quips I want to remember just so later and I find particularly surprising or interesting (or mistaken, hah).

When solving math problems, yes, by all means take notes! I find writing with a pen indispensable because it's much more flexible and expressive. And i need the memory caching that writing provides.