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Picture Name Schläfli symbol Vertex/Face configuration exact dihedral angle (radians) dihedral angle – exact in bold, else approximate (degrees) Platonic solids (regular convex)
The convex polyhedron is well-defined with several equivalent standard definitions, one of which is a polyhedron that is a convex set, or the polyhedral surface that bounds it. Every convex polyhedron is the convex hull of its vertices, and the convex hull of a finite set
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.
In an ideal polyhedron, all face angles and all solid angles at vertices are zero. However, the dihedral angles on the edges of an ideal polyhedron are nonzero. At each vertex, the supplementary angles of the dihedral angles incident to that vertex sum to exactly 2 π {\displaystyle 2\pi } . [ 2 ]
This dihedral angle, also called the face angle, is measured as the internal angle with respect to the polyhedron. An angle of 0° means the face normal vectors are antiparallel and the faces overlap each other, which implies that it is part of a degenerate polyhedron. An angle of 180° means the faces are parallel, as in a tiling. An angle ...
In geometry, a Platonic solid is a convex, regular polyhedron in three-dimensional Euclidean space. Being a regular polyhedron means that the faces are congruent (identical in shape and size) regular polygons (all angles congruent and all edges congruent), and the same number of faces meet at each vertex. There are only five such polyhedra:
Its vertex–center–vertex angle—the angle between lines from the tetrahedron center to any two vertices—is = (), denoted the tetrahedral angle. [9] It is the angle between Plateau borders at a vertex. Its value in radians is the length of the circular arc on the unit sphere resulting from centrally projecting one edge of the ...
In geometry, the rhombic dodecahedron is a convex polyhedron with 12 congruent rhombic faces. It has 24 edges, and 14 vertices of 2 types. As a Catalan solid, it is the dual polyhedron of the cuboctahedron. As a parallelohedron, the rhombic dodecahedron can be used to tesselate its copies in space creating a rhombic dodecahedral honeycomb.