1. Basic Geometry Concepts
Geometry Vocabulary
Basic Geometry Concepts

2. Example of How notes should look
Name____________________________
Date___________________Period_____
Geometry Vocabulary and Symbols
Unit 1
This side is for you to formulate questions at the end of class.
Conjecture
Is an unproven statement that is based on a pattern or statement

3. Geometry Vocabulary Conjecture
is an unproven statement that is based on a pattern or statement
Inductive Reasoning
is when you look for patterns and make conjectures

4. Geometry Vocabulary Counterexample
is an example that shows a conjecture is false
EX:
Statement: All birds can fly
Counterexample: Penguin

5. Geometry Vocabulary Undefined terms:
these are terms that cannot be mathematically defined using other known words
We must describe Point, Line, and Plane instead of defining them.

6. Point: Has NO dimension It is represented by a small dot
Geometry Vocabulary
Point:
Has NO dimension
It is represented by a small dot A
Point A

7. Geometry Vocabulary Line: Has ONE dimension
It extends without end in two directions
It is represented by a line with two arrowheads

8. LINE A B l
Name this line AB OR
Line l

9. Line: NOTE: For every two points there can be exactly one line formed
Geometry Vocabulary
Line:
NOTE: For every two points there can be exactly one line formed

10. Geometry Vocabulary Plane: Has TWO dimensions
It is represented by a shape that looks like a floor or a wall
You have to imagine that it extends without end in all directions.

11. PLANE D E F m
Name Plane
Plane DEF OR
Plane m

12. Geometry Vocabulary Plane:
NOTE: For every three non collinear points there exists one plane.

13. Geometry Vocabulary Space is a set of all points Postulates
Are statements that are acepted without further justification. This is a statement of fact

14. Congruent means the figures are exactly the same
Geometry Vocabulary
Congruent
means the figures are exactly the same

15. Geometry Vocabulary Collinear points Points that lie on the same line
Non Collinear points
Are points that do not lie on the same line.
Coplanar
Points and lines in the same plane

16. Ex. 1: Naming Collinear PointsD E F H
Name three points that are collinear
Solution:
D, E and F lie on the same line, so they are collinear.

17. Ex. 2: Naming Coplanar PointsH
Name four points that are coplanar.
Solution:
D, E, F, and G lie on the same plane, so they are coplanar. Also D, E, F, and H are coplanar; although, the plane containing them is not drawn. G E F D

18. Ex. 3: Naming Non Collinear PointsH
Name three points that are not collinear.
Solution:
There are many correct answers. For instance, points H, E, and G do not lie on the same line. G E F D

19. Geometry Vocabulary Segment-
Is the part of the line consisting of two endpoints. A B
Segment AB

20. Geometry Vocabulary Ray-
Is the part of the line consisting of one endpoint and all the points of the line on one side of the endpoint. A B
Ray AB

21. A B
Note that AB is the same as BA and AB is the same as BA. However, AB and BA are not the same. They have different initial points and extend in different directions.

22. If C is between A and B, then CA and CB are opposite rays.
Like points, segments and rays are collinear if they lie on the same line. So, any two opposite rays are collinear. Segments, rays and lines are coplanar if they lie on the same plane.

23. Ex. 4: Opposite Rays M Q X P N
Draw two lines. Label points on the lines and name two pairs of opposite rays.
Solution: Points P, Q, and X are collinear and X is between P and Q. So XP and XQ are opposite rays. M Q X P N

24. Geometry Vocabulary Intersection
The term intersect is used when lines, rays, line segments or figures meet, that is, they share a common point or points. The point or points they share is called the point of intersection. We say that these figures intersect.

25. Intersecting Lines
If two lines intersect then they intersect in exactly one point.

26. Line intersecting plane
If a line intersects with a plane then it intersect in exactly one point.

27. Plane intersecting Plane
If two planes intersect than they intersect at a line

28. Geometry Vocabulary Parallel Lines
Are coplanar lines that do NOT intersect

29. Geometry Vocabulary Skew Lines
Are noncoplanar lines; therefore they are NOT parallel and do not intersect

30. Geometry Vocabulary Perpendicular Lines
Are two lines that intersect to form right (90°) angle.