1. Points, Lines and Planes
Lesson 1 -2
Points, Lines and Planes

2. What are the undefined terms?
1) point
2) line
3) plane
The most fundamental concepts in geometry do not have precise definitions but, we understand their meanings intuitively. We say these concepts are undefined.
Geometry Leeson: Undefined Terms, Lines, Line Segments

3. . P . A(2,6) A point indicates a position or location in space.X Y
. A(2,6)
Points are named using capital letters and/or coordinates.
Geometry Leeson: Undefined Terms, Lines, Line Segments

4. A line is an infinite set of adjacent points.
Ex: Curved line
Naming a Line:
Two points on the line:
Single lowercase letter m A B C m
Ex: Straight line
The shortest distance between two points is a straight line.
Geometry Leeson: Undefined Terms, Lines, Line Segments

5. A plane is a set of points that forms a completely flat surface
A plane is a set of points that forms a completely flat surface. Two dimensions (length and width) Continues infinitely in all directions.
Naming a Plane:
Four points on the plane:
(can name with 3 pts.)
Single uppercase letter: D
Plane ABCD R
Plane R A B C

6. Defined Terms Space – the set of all points
Collinear points – points all in one line
Noncollinear – points not all in one line
Coplanar points – points all in one plane
Noncoplanar – points not all in one plane

7. INTERSECTS: meets or cuts
Intersection of two figures – set of all points in both figures
2lines intersect at a point
2 planes intersect at a line
3 planes intersect at a line or a point
A line intersects a plane at a point

8. Def: Collinear Points:
A collinear set of points is a set of points all of which lie on the same straight line. A B C D E
Points A, B, C and D are collinear.
Points A, E and C are not collinear.
Geometry Leeson: Undefined Terms, Lines, Line Segments

9. Drawing
Draw and label a picture of intersecting lines.

10. Drawing
Draw and label two planes that intersect in a line.

11. Drawing
Draw a line intersecting a plane in exactly one point.

12. Drawing Draw two parallel planes.
Are all horizontal planes parallel to one another?
Are all vertical planes parallel to one another?

13. Drawing Draw two vertical planes that are parallel to each other.
Draw to parallel planes that are not parallel to each other.