Geometry
posted by EKH on .
quadrilateral A B C D on a graph. Point A is at ( 5, 1), Point B is at ( 6, 1), Point C is at (4, 3), Point D is at (7, 5).
Prove the quadrilateral is a parallelogram by using Theorem 57; if the diagonals of a quadrilateral bisect each other, then it is a parallelogram. (Hint: Use the Midpoint formula.)

well, what are the diagonals?
AC and BD
midpoint of AC = (1/2,2)
midpoint of BD = (1/2,2)
Looks like the diagonals bisect each other.