Synthetic geometry of the real projective plane

ID: synthetic-geometry-of-the-real-projective-plane

Synthetic geometry of the real projective plane by Ciro Santilli 36 Updated +Created
It good to think about how Euclid's postulates look like in the real projective plane:
Unlike the real projective line which is homotopic to the circle, the real projective plane is not homotopic to the sphere.
The topological difference bewteen the sphere and the real projective space is that for the sphere all those points in the x-y circle are identified to a single point.
One more generalized argument of this is the classification of closed surfaces, in which the real projective plane is a sphere with a hole cut and one Möbius strip glued in.

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