Couldnt find anything from 15min of forum searching... If 2 objects are travelling along say, an x and y axis(or just 90 degrees apart really) at close to c, how do they interpret each others speeds? 0<theta<90 are easy enough. Couldnt find anything about perpendicular though. A newtonian version of this problem is simple enough but I am not sure when you are going at the speeds I am tlaking about.