1. Line- a straight path that goes in
two directions without ending.
A B
AB Read: “Line AB”
2. A ray has one end point and goes
on forever in only one direction.
CD Read: “Ray CD”
C D
We name ray by its endpoint and one of its points. Naming
a ray will always start on the endpoint.
3. A line segment has two endpoints.
EF
Read:
“Line Segment EF”
E F
6. Angle Parts
• An angle is a figure formed by
two rays with the same
endpoint.
• The common endpoint is
called the vertex of the angle.
• Each of the rays is a side of
the angle.
6
Vertex
7. Naming the Angle
• An Angle can be named in
one of three ways
• A number assigned to it
• It can be named after its
vertex (if there is only one
angle at that point)
• Using three points on the
angle (one from each side,
and the middle vertex)
section 1-4
7
1
G
D
B
O
∠1
∠B
∠DOG
∠GOD
8. Give four names for each
angle
1.) 2.)
section 1-4
8
A T
P
1
B I
F
3
**note: the numbers here are used to name the angle. If it were
meant to show the measure, it would have a degree symbol.
∠PAT ∠A ∠1 ∠TAP ∠IBF
∠B
∠3
∠FBI
9. Measure of an Angle
• An angle is measured in
units called degrees.
• The more the two rays are
separated from each other,
the greater the angle will
be.
• to describe the measure of
an angle we would say:
m∠1=22°
section 1-4
9
22°
41°
76°
120°
10. Types of Angles
• Angles are classified
by their measure
• Acute angles are less
than 90°
• Obtuse angles are
greater than 90°
• Right angles are exactly
90°
• Straight angles are 180°
10
12. Fill in the blanks using the figures.
•m∠BAC = ______
•Two names for
the obtuse angle
are ______ and
______.
section 1-4
12
F
E
H
110°
A
D
C
B
60°
20°
J
K
I
18°
60°
∠GFE
∠F 5
13. Fill in the blanks using the figures.
• ________ = 18°
• Two other names for
<H are ______ and
_______
• m∠DAC = _______
section 1-4
13
H
A
D
C
B
60°
20°
K
m∠I
∠5
∠ JHK
80°
15. 15
Determine the measurement of the following
angles and classify if they are acute, right, or
obtuse angle.
1.∠ROP 6. ∠TOS
2.∠POQ 7. ∠SOR
3.∠QOS 8. ∠UOQ
4.∠ROU 9. ∠SOU
5.∠TOP 10. ∠POR
