Schlegel Diagram of a Regular Tetrahedron

This example demonstrates the Schlegel diagram of a regular tetrahedron, a method of representing a 3D polyhedron by projecting it onto a 2D plane, showing the connectivity of vertices, edges, and faces. The core mathematical concepts include solid geometry, polyhedral projection, and the structure of a tetrahedron (four triangular faces, six edges, four vertices). The construction uses GeoGebra commands such as Circle, Intersect, Rotate, Point, Tetrahedron, Midpoint, Segment, Line, OrthogonalPlane, and Polygon to build the tetrahedron and its faces (e.g., zijvlakABC), with auxiliary points (E, F, G, H) and lines (f, g, h) to achieve the projection. This is suitable for high school or early university students learning about 3D-to-2D representations, and also useful for introductory computer graphics or topology courses.