The truncated tetrahedron is formed by **truncating** the vertices of a regular tetrahedron so as to leave the original faces hexagons.

REoo-apes-KaiSEKa, fourteen) formed by **truncating** the vertices of a cube so as to leave the original faces squares.

The truncated octahedron is formed by **truncating** the vertices of an octahedron so as to leave the original faces hexagons; consequently it is bounded by 8 hexagonal and 6 square faces.

Svo - Kat- rpoieKovra, thirty-two), is a 32-faced solid, formed by **truncating** the vertices of an icosahedron so that the original faces become triangles.

The truncated dodecahedron is formed by **truncating** the vertices of a dodecahedron parallel to the faces of the coaxial icosahedron so as to leave the former decagons.

The invention of the conic sections is to be assigned to the school of geometers founded by Plato at Athens about the 4th century B.C. Under the guidance and inspiration of this philosopher much attention was given to the geometry of solids, and it is probable that while investigating the cone, Menaechrnus, an associate of Plato, pupil of Eudoxus, and brother of Dinostratus (the inventor of the quadratrix), discovered and investigated the various curves made by **truncating** a cone.