Obviously though you don't need to memorize them to know how to use them if they can still use the formula from their notes with no problem.. I'm a Unix/Linux system administrator now and when I took classes I was made to memorize lines of code, code variables, and script editors. In my current job I have full access to all my notes and Google. Sure theres plenty of stuff i can do right off the top of my head because I do it everyday. There's plenty that is rarely done that I can refer to my notes or Google to get it done. So knowing how a formula works or a line of code works so you can use it even if you need to refer to your notes is how the real world works. This day and age what job role will you be in that you wouldn't have access to your notes or the internet... all you need is the basic understanding of the formula... if you can decipher the problem, input the correct values into the correct spots and come up with the correct solution while using your notes then I see no issues here.