You are strongly urged to make models to help with the section on polyhedra. To this end, you can get extra credit for making one or more of these basic models by Friday.

For the credit, the models don't have to be sculpture, but they should be a big enough size to see and make of something more substantial than notebook papers (manila folders work nicely).

Make a cardboard Model of a Regular Tetrahedron. Mark on the model the intersections of the planes of symmetry with the tetrahedron. Also, mark a cross section which is a square.

Make a cardboard Model of a Cube. Mark on the model the intersections of the planes of symmetry with the cube. Also, mark a cross section which is a regular hexagon.