Abstract
In order to understand how to classify projections of Platonic solids, we observe the elementary properties and symmetric relations of Platonic solids.Give a de nition of rotation groups and equivalent classes to classify the symmetries of Platonic solids, and ne the regularities of the classi cation.Finally, we get a simple way to classify the projections, and the target isextended to some polyhedrons with some speci c symmetric properties.