AlgTop4: More on the sphere

This lecture continues our discussion of the sphere, relating inversive geometry on the plane to the more fundamental inversive geometry of the sphere, introducing the Riemann sphere model of the complex plane with a point at infinity.

Then we discuss the sphere as the projective line over the (rational!) complex numbers.

This is the fourth lecture of this beginner's course in Algebraic Topology given by N J Wildberger of UNSW.

His YouTube site Insights into Mathematics at user: njwildberger also contains series on MathFoundations, History of Mathematics, LinearAlgebra, Rational Trigonometry and even one called Elementary Mathematics (K-6) Explained.