I was experimenting with some physics and the mathematics started to get a bit tougher than what I'm used to. I had a professor who looked at what I'm doing, offered to guide me, and told me to do some research on the variational principle. At the moment, I am in Calculus II. I did a couple searches, and the material I found is well beyond my knowledge at this moment. Can someone help direct me to a proper place to start on this study.