Answer: The diagonals of a parallelogram bisect each other. Steps (a), (b), and (c) outline proof of this theorem. (See Exercise 25 for a particular instance of this theorem.) (a) In the parallelogram OA BC shown in the figure, check that the coordinates of must be (b) Use the midpoint formula to calculate the midpoints of diagonals and (c) The two answers in part (b) are identical. This shows that the two diagonals do indeed bisect each other, as we wished to prove. (FIGURE CAN'T COPY)