Informal Geometry Review Home Page, Courses Menu,, Quarter Schedule, Grading Policy et. Informal Geometry Review I. Basic geometric notions A. Points, lines, and plane 1. Points, lines, and planes are basic, but undefined, terms. Space is the set of all points.
Collinear points are points that belong to the same line.
If three distinct points are collinear, then one of the points is between the other two. 4. Important subsets of lines are segments, half-lines and rays. A line segment consists of two points and all collinear points between them. Intersecting lines are two lines with exactly one point in common. Concurrent lines are lines that contain a single common point.