a point charge is the origin. with this point charge as the source point, what is the unit vector r in the direction of (a) the field point at x=0, y= -1.3m; (b) the field point at x=12.0 cm, y=12.0cm; (C) the field point x=-1.10 m, y= 2.60 m? express result in terms of unit vector i and j. show solution