1. A rear vision system for a vehicle, said rear vision system comprising: at least a rearward facing camera disposed at a rearward portion of a vehicle equipped with said rear vision system; wherein said rearward facing camera is operable to capture images rearward of the equipped vehicle; wherein, when a trailer is attached to the equipped vehicle and is rearward of the equipped vehicle, a processor is operable to process the captured images and, responsive at least in part to said processing, is operable to determine a trailer angle of the trailer relative to a longitudinal axis of the equipped vehicle; wherein said processor determines a location of a target at or of the trailer relative to the equipped vehicle and determines the trailer angle of the trailer responsive to the determined location; and wherein the target comprises at least one of (a) an icon or shape or indicia disposed at a forward portion of the trailer, (b) an icon or shape or indicia established on a sheet attached at a forward portion of the trailer, (c) an icon or shape or indicia established at a forward portion of the trailer, (d) a target pattern established at a surface of the trailer or trailer tongue, (e) a colored pattern established at a surface of the trailer or trailer tongue and (f) a forward portion of the trailer.