the vector from A to C=(-6,2) so the vector from the midpoint is (-3,1) hence since BD is perpendicular the vector from the centre to eith B or D is (1,3) hence the coordinates are (4,3)+(1,3)=(5,6) or (4,3)-(1,3)=(3,0)
the above, wat is the concept called? the concept which states abt the sign switching and vectors..just wanted to know so i can look it up and learn it.! plz help