1. Chapter 1.2 Points, Lines, And Planes
Geometry

2. Point: ∙𝑨 (𝑷𝒐𝒊𝒏𝒕 𝑨) Line: 𝒍𝒊𝒏𝒆 𝑨𝑩, 𝑨𝑩 ,𝒍𝒊𝒏𝒆 𝒕 A Location in Space
Has No Size
Name a point with a CAPITAL LETTER and represent it with a dot
∙𝑨 (𝑷𝒐𝒊𝒏𝒕 𝑨)
Line:
Straight Path of Points
No Thickness
Extends Infinitely in Opposite Directions
𝒍𝒊𝒏𝒆 𝑨𝑩, 𝑨𝑩 ,𝒍𝒊𝒏𝒆 𝒕 t A B

3. Collinear: Noncollinear: B A C B A C Three or more points on a line.
Points do not form a line. B ● A C ● B ● ● A C

4. Ex.1) Identify Collinear Points
Are the following points collinear?
A, E, C
G, F, B
D, E, A
Name line m in three other ways
Name line l in three other ways

5. PLANE X Plane RST or Plane X R . S . T . Flat Surface/No Thickness
Infinite Number of Points and Lines
Extends Without End
Any 3 Noncollinear Points ALWAYS Make a Plane
Name a Plane
A Capital Letter or
At Least 3 of its Noncollinear Points
R . S .
T . X
Plane RST or Plane X

6. Ex.2) Name the Plane A B D C E F H G The Bottom The Top The Front
The Back
The Left Side
The Right Side

7. COPLANAR
Lines or points in the same plane.
R . S . T. X

8. Through any 2 points there is exactly one line.B t
Line t is the only line that passes through points A and B.
Postulate 1-1
Two lines intersect in exactly one point. ● P m n
Lines m and n intersect at point P.
Postulate 1- 2

9. A line and a plane intersect, in exactly one point.

10. Two planes intersect, in exactly one line.
Postulate 1-3
Plane ABC and Plane D
intersect at line t.
Two planes intersect, in exactly one line. ●C ●A ●B D t

11. Picture this cube as having Planes M, L and P
Picture this cube as having Planes M, L and P. They intersect in 3 separate lines. L P M

12. 𝐸𝐻 Ex.3) A B D C E F H G Name the intersection of Planes ABC & BFG
Name two planes that intersect the given line. 𝐸𝐻

13. Through any 3 noncollinear points there is exactly one plane.
Postulate 1-4
Through any 3 noncollinear points there is exactly one plane. A G H F E D C B
Can you name sets of noncollinear points?

14. A G H F E D C B
Find Planes:
ABC
HEF
BCG
ADG

15. Ex.4) Shade the plane containing points A, E, FB
Shade the plane containing points A, E, F
Name another point in Plane EHG
Is point F coplanar with plane DCG?