Editing Hyperplane (section)

== Dihedral angles ==

The [[dihedral angle]] between two non-parallel hyperplanes of a Euclidean space is the angle between the corresponding [[normal vector]]s. The product of the transformations in the two hyperplanes is a [[rotation (mathematics)|rotation]] whose axis is the [[Euclidean subspace|subspace]] of codimension&nbsp;2 obtained by intersecting the hyperplanes, and whose angle is twice the angle between the hyperplanes.

===Support hyperplanes===
A hyperplane H is called a "support" hyperplane of the polyhedron P if P is contained in one of the two closed half-spaces bounded by H and <math>H\cap P \neq \varnothing</math>.<ref>Polytopes, Rings and K-Theory by Bruns-Gubeladze</ref> The intersection of P and H is defined to be a "face" of the polyhedron. The theory of polyhedra and the dimension of the faces are analyzed by looking at these intersections involving hyperplanes.