A polyhedron
There are not only prisms and pyramids! This (non-convex) polyhedron has 10 faces, all of them have the shape of an equilateral triangle, 7 vertices and 15 edges (and 10-15+7=2); its type of symmetry is the same of a pyramid with triangular base.
© matematita
The image belongs to the sections...:
Prisms, antiprisms, pyramids, dipyramids (3D geometry)
