1. Points, Lines and Planes Lesson 1.2 Pre-AP Geometry

2. Points, Lines, and Planes The three most basic figures in geometry are points, lines, and planes. This lesson illustrates how these three basic figures relate to one another.

3. Objectives 1.Use the undefined terms point, line, and plane. 2.Draw representations of points, lines, and planes. 3.Use the terms collinear, coplanar, and intersection.

4. Vocabulary Point A geometric element that has position but no dimension. A point is defined by its coordinates. Symbol: · A Line A line can be described as an ideal zero-width, infinitely long, perfectly straight curve containing an infinite number of points. Symbol: (The term curve in mathematics includes "straight curves")

5. Vocabulary Plane A plane is a two-dimensional surface that is perfectly flat, is infinitely vast, and infinitesimally thin. Undefined term A term, such as point, line, plane, and space, that is accepted without definition.

6. Vocabulary Space The set of all points. The unlimited area which extends in all directions and within which all things exist. Intersect To meet or cross at a point.

7. Vocabulary Collinear Lying on the same straight line. Collinear points lie along a straight line. Any two points are always collinear. Coplanar Lying in the same plane. A set of points in space is coplanar if the points all lie in the same plane. Note: Collinear points are automatically coplanar, but coplanar points are not necessarily collinear.

8. Points Things that we can use to represent a point: a marble

9. Lines Things that we can use to represent a line: a taut piece of string

10. Plane Things that we can use to represent a plane: a sheet of paper a poster board

11. Intersecting Planes Things that we can use to represent intersecting planes: the sides of a cardboard box

12. Practice Quiz - True or False 1. ends at P. 2.Point S is on an infinite number of lines. 3.A plane has no thickness. 4.Collinear points are coplanar. 5.Planes have edges. 6.Two planes intersect in a line segment. 7.Two intersecting lines meet in exactly one point. 8.Points have no size.

13. Problem Set 1.2 Written Exercises p.7: # 2 – 26 even, 27 - 36