Extended side Pentagon Angle Sum

A pentagon tray that holds triangles each layed off at right angles so if a side was extended like the actual design, you can see two right angles. If you take the triangles and place them with each of their smallest angles ( 18 degrees ) and stuff them into the exterior angle created from the extended wall you will notice the 5 triangles in the tray of the pentagon can demonstrate that their smallest angles all added together equal a right angle.
This was my original idea meaning I actually made this thing and did not copy anyone, that said; I did derive this from a geometry homework problem from Dan Jackson's class. The homework problem makes you prove how if you extend every wall of the pentagon once each in the same direction creating 5 exterior angles, that those 5 exterior angles add up to 4 right angles. Thanks for reading if you did, and I hope you enjoyed this concept and maybe learned something.