Suppose an electric charge p(x, y) is uniformly spread on a disc of radius r around the origin. use maxwell's first equation (in a non-dimensional version) (4) v e = p from the origin r > r, the field is proportional to r-1. that far to prove away do not use the explicit formula for the electric field. do use the fact that the electric field points towards the charged particle, and whatever symmetries this problem has.