Hi. I have this problem with differentiating vectors. Primarily because I have no experience at all (or whatsoever) about differentiating vectors. I am at a total loss here. I even have no idea regarding the difficulty of this (thus the [ I ] prefix). Please help me. How did the two equations below come out? Can someone show me formulas on how did these appear? What happened to the T? I did search for resources over the net about formulas and I got even more confused. The bolded variables are matrices... or vectors. I think.