# What other theorems about the duality of projective geometry?

As the real projective plane, PG(2, R), is self-dual there are a number of pairs of well known results that are duals of each other. Some of these are:

Desargues' theorem ⇔ Converse of Desargues' theorem
Pascal's theorem ⇔ Brianchon's theorem
Menelaus' theorem ⇔ Ceva's theorem

I get some dual theorem in wiki. So besides the above theorem, is there any other theorem about duality in projective space? Thank you.

Since you mentioned Pascal $$\iff$$ Brianchon, see Chapter XIV for that and two other biggies: Carnot's Theorem and its correlative, and Desargues' Theorem (the 'other' Desargues' theorem about transversals through systems of conics) and its correlative).