Online Geometry Problem 659: Parallelogram, Parallel Lines, Collinear Points. Level: High School, Honors Geometry, College, Mathematics Education

The figure shows a parallelogram ABCD, E is on the extension of BD. CF and AE are parallel. AF and CE meet at G. GH is parallel to AD and CH is parallel to BD. Prove that the points D, H, and F are collinear. See also: Artwork Problem 659.