Lesson 1.2 Intro to Geometry

Learning Target I can understand basic geometric terms and postulates.

1. Points Points do not have actual size. How to Sketch: Using dots How to label: Use capital letters A B

2. Postulates An accepted statement of fact.

3. Line POSTULATE – Through any two points there is exactly ONE line Lines extend indefinitely and have no thickness or width. How to sketch : using arrows at both ends. How to name: 2 ways (1) small script letter – line n (2) any 2 points on the line - Never name a line using three points - n A B C

A part of a line that consists of two endpoints and all the points in between them. How to name: by 2 endpoints 4. Segment A B C

A part of a line that consists of one endpoint and all the points to one side of that endpoint. 5. Ray A B C How to name: 2 points with ENDPOINT FIRST Not like this…

6. Collinear Points ABC A B C Collinear Non collinear Collinear points are points that lie on the same line.

7. Planes POSTULATE – Through any 3 non- collinear points there is exactly ONE plane A plane is a flat surface that extends indefinitely in all directions. How to sketch: Use a parallelogram (four sided figure) How to name: 2 ways (1) Capital script letter – Plane M (2) Any 3 non collinear points in the plane - Plane: ABC or BCA or BAC, etc. A B C M

Different planes in a figure: A B CD E F G H Plane BCG Plane ABF Plane CDH Etc.

Other planes in the same figure: Any three non collinear points determine a plane! Plane ACG Plane ACH Etc.

8. Coplanar Objects Coplanar objects (points, lines, etc.) are objects that lie on the same plane. Are the following points coplanar? A, B, C ? A, B, C, F ? H, G, F, E ? E, H, C, B ? A, G, F ? C, B, F, H ? Yes No Yes No

9. Intersection of Two Lines POSTULATE The intersection of two lines is a point. m n P Line m and line n intersect at point P.

10. Intersection of Two Planes POSTULATE P R A B Plane P and Plane R intersect at the line The intersection of two planes is exactly ONE line.