Three point charges are arranged at the corners of a square of side L. What is the potential at the fourth corner (point A), taking V = 0 at a great distance? OK, I am very confused. First of all, Giancoli (my textbook) seems to explain how to do this for one point charge, but I am confused about doing this for three charges. Second, what do they mean by "at a great distance"? I am assuming I would want to use V = 1/4piE0 Q/r. So I am guessing that I would have to do some kind of vector deal? Help appreciated.