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The (n − 3)-faces of an n-polytope are called peaks. A peak contains a rotational axis of facets and ridges in a regular polytope or honeycomb. For example: The peaks of a 3D polyhedron or plane tiling are its 0-faces or vertices. The peaks of a 4D polytope or 3-honeycomb are its 1-faces or edges.
In geometry, a polyhedron (pl.: polyhedra or polyhedrons; from Greek πολύ (poly-) 'many' and ἕδρον (-hedron) 'base, seat') is a three-dimensional figure with flat polygonal faces, straight edges and sharp corners or vertices.
In a polyhedron or more generally a polytope, an edge is a line segment where two faces (or polyhedron sides) meet. [3] A segment joining two vertices while passing through the interior or exterior is not an edge but instead is called a diagonal. An edge may also be an infinite line separating two half-planes. [4]
The dimension of a face is the dimension of this hull. The 0-dimensional faces are the vertices themselves, and the 1-dimensional faces (called edges) are line segments connecting pairs of vertices. Note that this definition also includes as faces the empty set and the whole polytope P. If P itself has dimension d, the faces of P with dimension ...
The property of having a similar arrangement of faces around each vertex can be replaced by any of the following equivalent conditions in the definition: The vertices of a convex regular polyhedron all lie on a sphere. All the dihedral angles of the polyhedron are equal; All the vertex figures of the polyhedron are regular polygons.
These edges form square faces, making the dihedral angle of a cube between every two adjacent squares being the interior angle of a square, 90°. Hence, the cube has six faces, twelve edges, and eight vertices. [2] Because of such properties, it is categorized as one of the five Platonic solids, a polyhedron in which all the regular polygons ...
[3]: 9 If a face contains a single point {v}, then v is called a vertex of P. If a face F is nonempty and n-1 dimensional, then F is called a facet of P. Suppose P is a polyhedron defined by Ax ≤ b, where A has full column rank. Then, v is a vertex of P if and only if v is a basic feasible solution of the linear system Ax ≤ b.
Vertex, edge and face of a cube. The Euler characteristic χ was classically defined for the surfaces of polyhedra, according to the formula = + where V, E, and F are respectively the numbers of vertices (corners), edges and faces in the given polyhedron. [2]