This document defines and describes basic geometric terms including points, lines, planes, and their intersections. It discusses concepts such as collinear points lying on the same line, coplanar points lying on the same plane, line segments consisting of endpoints and points between them, and opposite rays extending from the same point on opposite sides of another point. Examples are provided to illustrate these geometric concepts and relationships between points, lines, and planes.

1. 1.2 Points, Lines, & Planes Objectives: - Understand and use the basic terms of geometry - Sketch the intersection of lines and planes

2. Point Has no dimension Usually represented by a small dot The intersection of two lines is a point .A Point A

3. Line Extends in one dimension Usually represented by a straight line with 2 arrowheads to indicate that the line extends without end in two directions The intersection of two planes l A B <-------------------------------------------------------> <--> Line l or AB

4. Plane Extends in two dimensions Usually represented by a shape that looks like a tabletop or wall. You must imagine that the plane extends without end, even though the drawing of a plane appears to have edges Plane M or Plane ABC A B C M

5. More Concepts A point lies on a line or a plane Collinear points - points that lie on the same line Coplanar points - points that lie on the same plane

6. Example Which 2 points are collinear? Which 3 points are coplanar? Name 2 points that are not collinear. Name 3 points that are not coplanar Q A B C M

7. More concepts A point on a line is between two other points on the line. Consider the line AB. ( AB ) The line segment or segment AB ( AB ) consists of the endpoints A and B, and all points on line AB that are between A and B. The ray AB ( AB ) consists of the initial point A and all points on line AB that lie on the same side of A as point B. A B

8. More concepts Note that line AB is the same as line BA, and segment AB is the same as segment BA, but ray AB is different from ray BA. If C is between A and B, then ray CA and ray CB are opposite rays. A B C

9. In your notes . . . Draw 3 noncollinear points, J, K, and L Draw JK Draw KL Draw LJ

10. Another example . . . Name two pairs of opposite rays: X M N Q P

11. Intersections Two or more geometric figures intersect if they have one or more points in common. The intersection of the figures is the set of points the figures have in common. See page 12

12. Do p. 13 1-8 together Homework: Worksheets