chapter "Rotational Symmetries of the Tetrahedron" theory Tetrahedron imports Orbit_Stabiliser begin section "Definition of the Tetrahedron and its Rotations" text ‹ In this section we will use the orbit-stabiliser theorem to count the number of rotational symmetries of a tetrahedron. The tetrahedron will be defined as a set of four vertices, labelled A, B, C, and D. A rotation is defined as a function between the vertices. ›