1. The problem statement, all variables and given/known data I need to derive some equation that are on the paper "does the inertia of a body depend on it's energy content". http://www.fourmilab.ch/etexts/einstein/E_mc2/www/" [Broken] I just dont know where to start and if someone can point me to the right direction, it will be so much help. The first is, I know that this was derived using the theory of relativity but I don't know where to start and transformations to use. The second is, The emission of waves of light and other stuffs just confuses me more, and is these just using the above relationship? Thank you very much.