Pentagon Geometry

My partner and I, Kevin miller, created this design together in Dan Jackson's college geometry class. It is a pentagon that has a single wall extended with 5 90 degree triangles on the inside. If you take the 5 triangles and put the acute angles all adding together, 4 of them plus the one adjacent left inside will equal to 90 degrees. That would be 18x5. We derived this design from a homework problem where you must prove that if you extend all 5 walls of the pentagon then those exterior angles created from doing so will equal 4 right angles.