The document defines three fundamental geometric terms: points, lines, and planes. It provides the following definitions: - A point is a location in space that has no dimensions. It is usually represented by a dot and named with a capital letter. - A line is a one-dimensional object that extends infinitely in both directions. It is straight and can be named using a lowercase letter or two points on the line. - A plane is a two-dimensional surface that extends infinitely in both directions. It contains an infinite number of points and lines. It is usually represented by a four-sided figure and can be named with a capital script letter or three points on the plane. The document then provides

1. 1.2 Points, Lines, and Planes

2. What is a definition?
 Known words used to describe a new word
Undefined terms – are terms not formally
defined.
There are three undefined terms in geometry:
1. Point 2. Line 3. Plane

3. Point
1. A location in space.
2. Has no dimension (no length, no width, no
depth).
3. Usually represented by a dot.
4. Named using one capital letter.

4. Point
For example:
●B

5. Line
1. A series of points that extends in opposite
directions without end.
2. One-dimensional (length).
3. Has an arrowhead on each end
representing the fact that it goes on
forever.
4. Always straight.
5. Named with a lowercase script letter or by
2 points on the line

6. Line
A B
l
Can be called:
Line l
Line AB or AB
Line BA or BA
For example:

7. Plane
1. A flat surface that extends forever in two
dimensions (length & width).
2. Contains infinitely many points and lines.
3. Usually represented by a four-sided
figure.
4. Named with a capital script letter or 3
points on the surface of the plane

8. Plane
A
B
C
W Can be named:
Plane W
Plane ABC, plane BCA, plane
CBA, etc.
For example:

9. More Definitions
 Collinear points –
points that can lie on the same
line.

10. More Definitions
 Noncollinear points –
D

11. More Definitions
 Coplanar points –
points that can lie on the same plane.

12. More Definitions
 Noncoplanar points –
D
A

13. More Definitions
 Equidistant – equally distant

14. More Definitions
 Intersect –
Two or more figures intersect if they
have one or more points in common.
 Intersection –
All points or sets of points the
figures have in common.

15. When a line and a point intersect,
their intersection is a point.
B
l

16. When 2 lines intersect, their
intersection is a point.

17. When 2 planes intersect, their
intersection is a line.

18. When a line and plane intersect, their
intersection is a point.

19. Questions???

20. Classify each statements as true or
false
REMOTE TIME !

21. Question 1
 PF ends at P

22. Question 2
 Point S is on an infinite number of lines

23. Question 3
 A plane has no thickness

24. Question 4
 Collinear points are coplanar

25. Question 5
 Planes have edges

26. Question 6
 Two planes intersect in a line segment

27. Question 7
 Two intersecting lines meet in exactly one point

28. Question 8
 Points have no size

29. Question 9
 Line XY can be denoted as XY or YX.

30.  Horizontal Planes – Ceiling and Floor
 Horizontal Planes – Two sides horizontal and
no sides vertical

31.  Vertical Planes – Walls
 Vertical Planes – two sides are vertical

33. Group Practice
Vertical line l intersects a horizontal plane M at point O
l
M
O

34. Group Practice
Horizontal plane Q and vertical plane N intersect

35. Group Practice
Point P is not in Plane N. Three lines through point P
intersect N in points A, B, and C.

36. True or False
 All points on a line are coplanar

37. True or False
 A line has one endpoint

38. True or False
 A point is named by a capital letter.

39. True or False
 Two lines intersect in two points.

40. True or False
 The edge of a plane is a line.