Oddly enough, i forget my geometry laws two days before the test. If ABCD is a parallelogram where x and y are on the midpoints of AD and BC. Prove that BX and DY are parallel. I understand one would have to prove that corresponding angles are equal. thus, AHX would equal CMY, and ADM would equal BHC. My question is: if a large triangle and a smaller triangle have proportional sides (e.g. 1/2), would the angles be proven equal?