Betweenness and Elementary Figures

Abstract

In Chapter 2 we introduced the Euclidean Plane model using ideas from analytic geometry as our motivation. This was useful at that time because it was the most intuitive method and led to simple verification of the incidence axioms. However, treating vertical and non-vertical lines separately does have its drawbacks. By making it necessary to break proofs into two cases, it leads to an artificial distinction between lines that really are not different in any geometric sense. Furthermore, as we develop additional axioms to verify we will need a more tractable notation. For these reasons we introduce an alternative description of the Euclidean Plane, one that is motivated by ideas from linear algebra, especially the notion of a vector.