1. Lesson 1.2
Intro to Geometry

2. Learning Target
I can understand basic geometric terms and postulates.

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

4. Lines
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

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

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

7. Opposite Rays
Two rays that share the same endpoint and form a straight line. A B C

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

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

10. Postulates
An accepted statement of fact.

11. Line POSTULATE – Through any two points there is exactly ONE lineB

12. 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 M B C

13. Different planes in a figure:B
Plane BCG
Plane ABF
Plane CDH
Etc. D C E F H G

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

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

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