Given a line L in the projective plane, what is its dual point?

Let P be a configuration of n points in the projective plane, not all on a line.

Since the projective plane has a large enough symmetry group, they are in no way special, though.

This example is known as the projective plane of order three.

Lines in the projective plane are defined exactly as above.

The number N is called the order of the projective plane.

In particular, if , then the difference set gives rise to a projective plane.

The set of all such lines is itself a space, called the real projective plane in mathematics.

The proof that there is no finite projective plane of order 10.

These lines are now interpreted as points in the projective plane.