I am struggling with how much math do to on the whiteboard during lectures, and of how much can be put on slides (to which the students have access) instead of me writing everything in detail. I have found a very interesting discussion at www.mathoverflow.net/questions/80056/using-slides-in-math-classroom, but I would like some perspective from lecturers in physics. I find that writing everything on the whiteboard takes up a lot of time, coupled with the fact that I have to pause to let the students finish copying everything. Often, I find that doing the derivation can be instructive if one tries to do it themselves, otherwise the answer is sufficient. (If anyone is aware of research on whether copying down mathematical developments helps in learning, I would appreciate some references.) At the same time, going through slides sometimes feels like just having symbols dancing around on the screen. with students not really following what is going on.