Above is a picture of a net of 5-cells polytope. This polytope is a 4-dimensional
regular pyramid. Each cell of this polytope is a regular tetrahedron (see
Plato’s polyhedrons). A
construction of such net is not unique. This time a net is a regular tetrahedron
W and 4 the same regular tetrahedrons glued to each face of W. These 4
tetrahedrons hide tetrahedron W, hence W cannot be seen.
There is an easy explanation how to receive a regular 5-cells polytope from this
net. Consider 4 outer tetrahedrons of this net. In 4-dimensional space they can
be rotated about the face common with W. Let us rotate them the way that all
outer vertices coincide and we’ll receive required polytope.
Let us present another net of this polytope:
All cells are seen on this picture now.
Let us turn to 8-cells regular polytope. It is also called hypercube. Let us present 2 pictures of a net of this polytope:
As before this net is not unique. Let us show another way of construction:
Only 7 cells are seen on this picture. It is left to our viewers to decide how
to place 8-th cell.