Download Geometry: Section 1.1 Name:

Geometry: Section 1.1
Name:
Objective: To define and name points, lines, rays, segments, angles
and triangles.
Points: A point represents location. It has no size and is always named
by a capital letter.
Line: By line we mean a straight line composed of infinitely many
points extending infinitely far in opposite directions.
Naming a line:
1) Use a small cursive letter near the line.
ˆm
2) Use any two points on a line, with line symbol above them.
B
C
D
Using this method,
there are 6 ways to name this
!line.
##" Finish them below.
CB ,
,
,
,
A line may be marked consistently with tick marks and numbers and
become a number line.
Line segments: A line segment or segment is a part of a line with two
definite endpoints. It is named by its endpoints, with a segment symbol
above the two endpoints. They are subsets of lines.
Name these segments.
A
E
D
C
F
G
B
Rays: A subset or part of a line which has one endpoint and goes
forever in one direction. They are always named by the endpoint first
and then any other point on the ray with a ray symbol above the two
letters. A
C
E
F
B
D
Angle: the union of two rays with a common endpoint. The common
endpoint is called the vertex and the rays form the sides of the
angle.
Way to name angles:
1) An angle can be named by a number written inside the
angle (with no degree sign)
A
2
B
!2
C
2) An angle can be named by its vertex
A
C
B
!B
3) An angle can be named by three points on the angle, but the
vertex must be the middle point.
H
A
2
1
B
! ABC
Name ! 1 and ! 2.
! 1 can be named
C
! 2 can be named
Why must three letters be used to name these angles?
Triangle: The union of three segments with common endpoints.
The endpoints are called the vertices of the triangle. The segments
are the sides of the triangle. We name a triangle by its three
vertices. ∆ABC or ∆ACB or ∆CAB, etc.
A
B
! ABC = AB ! BC ! AC
C
Homework: 1.1, pg. 7-8, # 1, 3, 5-14 all