I need to write Mathematics, but I would like to avoid Latex for quick notes that I wish to send to colleagues. So I would like to have somewhere to write with some sort of pen, in such a way that
1) what I write appears on the display of my computer (please note that I don't have an iPad, just a Macbook)
2) it gets saved on my computer when I finish.
These are just quick notes, so no special drawing features are required (on the contrary, the simpler/cheaper the better).
What should I consider? Since I own a Macbook, also writing on the built-in trackpad would be fine, but I've heard that the Inklet app slows down the computer in a very nasty way...
Thank you very much in advance.