A polyhedron
A tetrahedron with two faces with the shape of equilateral triangles (the red ones in the model) and two faces with the shape of rectangle isosceles triangles (the green ones). You can see a net of this tetrahedron.
Four of these polyhedra form a regular octahedron, as we can see also by placing a tetrahedron between a pair of perpendicular mirrors.
© matematita
The image belongs to the sections...:
Puzzles involving reconstruction of polyhedra (3D geometry)
