Projective space
Dual projective space
The dual projective space Sπ¨π© of an π-dimensional abstract projective space S has (π βπ β1)-dimensional subspaces of S as its π-dimensional subspaces,
and the containment relation is reversed, geo
e.g. hyperplanes of S are the points of Sπ¨π©.
By the principle of duality,
any theorem stated in terms of incidence, subspaces, and containment which follows from the axioms of an abstract projective space S also hold for its dual Sπ¨π©.1
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