### MathFoundations26: The basic framework for geometry (IV)

Angles don't make sense in the rational number system. The proper notion of the separation of two lines is the `spread' between them, which is a purely algebraic quantity and can be calculated easily using rational arithmetic only. This video highlights some of the advantages in replacing `angle' with `spread'. It also gives an explicit formula for the `inverse cosine' function, which rarely appears in trigonometry texts, despite the universal reliance on this function via calculators.This lecture is part of the MathFoundations series, which tries to lay out proper foundations for mathematics, and will not shy away from discussing the serious logical difficulties entwined in modern pure mathematics. The full playlist is at http://www.youtube.com/playlist?list=PL5A714C94D40392AB&feature=view_all

Length:
06:52