A polyhedron
A pyramid with a rhombus with angles 60° and 120° as a base and four triangles (two equilateral triangles and two rectangle isosceles triangles) as lateral faces. Here you can see a net.
We can construct this polyhedron by putting together a regular tetrahedron and anothertetrahedron, of equal volume.
It is slightly more difficult to see how to dispose four of these polyhedra, paired in this way, in order to make a regular tetrahedron.
© matematita
The image belongs to the sections...:
Puzzles involving reconstruction of polyhedra (3D geometry)