Different shapes and Origami
(the world of 2-dimensions)
(1) Folding Equi-polygon
When you fold a sheet of paper you will get all kinds of different shapes. There are polygons that have the equal sides and angles. Try some of these.
(a) An equilateral triangles
(b) A square
(c) A pentagon
When the diagonals of the pentagon are 2 in portion, their sides would be √5−1. It will leads you to fold the pentagon
(d) If you are interested in this, you can check other references.