Geometry Problem 603: Parallelogram, Diagonals, Congruence, Concurrency
The figure shows a parallelogram ABCD.
E is on DA extended, F is on DC extended, G is on BC extended,
and H is on BA extended. If EFGH is a parallelogram, prove that
lines AC, BD, EG, FH, MN, and PQ are concurrent.
Geometric Art of problem 603: Generative abstract compositions