10: Orthocenters exist! Video Lecture:

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10: Orthocenters exist!
This is a video lecture course on Hyperbolic Geometry by Prof. N J Wildberger of the School of Mathematics and Statistics, University Of New South Wales, Australia. This is a complete and relatively elementary course explaining a new, simpler and more elegant theory of non-Euclidean geometry; in particular hyperbolic geometry. It is a purely algebraic approach which avoids transcendental functions like log, sin, tanh etc, relying instead on high school algebra and quadratic equations. The theory is more general, extending beyond the null circle, and connects naturally to Einsteins special theory of relativity. This course is meant for mathematics majors, bright high school students, high school teachers, engineers, scientists, and others with an interest in mathematics and some basic algeb