3.3 LessonB

RULER – measures_________________PROTRACTOR – measures ______________*coordinate – For every point on a line there corresponds exactly 1 real number called its coordinate.* coordinate – For every ray in a half rotation there correspond exactly 1 real number called its coordinate,The Ruler Postulate: The points on a line can be numbered so that positive number differences measure distance!The Protractor Postulate: The rays in a half rotation can be numbered from 0-180, so that positive number differences measure angles!Def – Betweenness of Points: A-B-C iff ab>c.Def – Betweenness of Rays: OA-OB-OC iff ab>cThm1 – Betweenness of Points Thm: If A-B-C, then AB + BC = ACThm2 – Betweenness of Rays Thm: If OA-OB-OC, then AOB + BOC = AOC