# polarFace -- computes the dual face of the polar polyhedron

## Synopsis

• Usage:
fv = polarFace f
• Inputs:
• Outputs:
• fv,

## Description

Given a polyhedron f which is a face of a polyhedron P the function polarFace computes the polar P' of P and the corresponding face of P' on which all points of f attain their minimum. Note that this function only works correctly for polyhedra with the origin in its relative interior.

 i1 : P = hypercube 3 o1 = P o1 : Polyhedron i2 : f = first faces(1,P) o2 = ({0, 2, 4, 6}, {}) o2 : Sequence i3 : f = convexHull (vertices P)_(f#0) o3 = f o3 : Polyhedron i4 : fv = polarFace(f, P) o4 = fv o4 : Polyhedron i5 : vertices fv o5 = | 1 | | 0 | | 0 | 3 1 o5 : Matrix QQ <--- QQ

If f is not a face of another polytope, then it considers f as a face of itself. Thus, it computes the polar of f, and returns the empty polyhedron as a face of the polar of f.

 i6 : P = hypercube 3 o6 = P o6 : Polyhedron i7 : polarFace(P, P) o7 = Polyhedron{...1...} o7 : Polyhedron

## Ways to use polarFace :

• "polarFace(Polyhedron,Polyhedron)"

## For the programmer

The object polarFace is .