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We already know by Theorem 5.2 that the equation holds on the set of vertices. Furthermore it is clear from the definition, that is supported on the vertices of . What remains to show is that this also holds for .
Let . We want to show . Let be the open faces of of dimension at least one. For every there is a such that for all there exists such that . Furthermore for some and and we define . Now let . Then there is an such that . For and as above it follows
hence
A similar argument shows
and hence
We conclude and lies in a hypersurface which depends on but not on . Hence is contained in the union of hypersurfaces. Therefore