I saw a web-site someday -- it had lots of codes for formulas from many fields of knowledge -- all categorized and searchable. So that when You teach, say, electrodynamics You could come there and get the code for Maxwell equations right away. I lost the linke and can't find the web-site any more.
Do You happen to know some sites like that?
summary of solutions:
- Go to wikipedia, find the equation, copy its image as text with Ctrl-c -- and LaTeX code of image gets into the clipboard.