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E
Q
W
R
S
Y
1. Name a plane.
2. Name a line.
3. Name a ray.
4. Name a point.
5. Name three collinear
points.
T
6. Name four coplanar points.
7. Name a segment.
8. Do points T and Q lie on the
same line?
9. Plane RYT  plane EWTR is
_______.
10. How many planes does
point S lie on?
Homework Answers
pg. 15
5) True
6) False
7) True
8) True
9) False
10) True
11) False
12) True
13) True
14) False
15) True
16) False
17) False
18) True
pg. 16
33) x = 6
34) x = 11
35) x = 3
36) x = 7
37) y = 6
38) y = 7
39) z = 8
GE = 10, EH = 10
E is the midpoint of GH
40) z = 5
GE = 5, EH = 6
E is not the midpoint of GH
In this section we will discuss the
proper notation of angles, specific
classifications of angles, and the
properties of angle bisectors and the
Angle Addition Postulate.
Sides
Angle – the figure
formed by two rays that
have the same endpoint.
C
Vertex
T
A
The two rays are
called the sides; the
shared endpoint is
called the vertex.
We name an angle using three letters
and the  symbol.
Acceptable:
C
CAT
A
T
TAC
Unacceptable:
ACT
TCA
Order Matters!! The vertex must be
the letter in the middle!
Alternative Notation
C
B
A
T
CAB
CAT
BAT
You can name an angle
just with the vertex.
This angle could be A.
Sometimes using only one
letter may not be specific
enough, because it may refer
to more than one angle.
IF THERE IS ANY DOUBT,
USE THREE LETTERS!
We also may name angles with
numbers.
C
B
A
1
2
T
CAB is 1
BAT is 2
Measuring Angles
We measure angles using a protractor.
The units for angle measurement is
degrees.
Symbol for Degree:
70°
Measure of Angle:
mABC
Measure Angles #1-9 using
your protractor.
Estimate to the nearest
degree.
Classifying Angles
Acute Angle
An angle measuring
between 0 and 90.
Obtuse Angle
An angle measuring
between 90 and 180.
Right Angle
An angle measuring
exactly 90.
Straight Angle
An angle measuring
exactly 180.
A pair of opposite rays creates
a straight angle.
Angle Interior
Any points that lie inside the angle.
T
B
A
H
C
D
E
Congruent Angles
Recall the Definition of Congruent:
Figures that are the same shape and size.
Congruent Angles – angles that have
equal measures.
Remember:
M
Figures can be
congruent;
Z
measures can
P
120°
be equal.
T
120°
I
A
MAT
@
ZIP
mMAT
= mZIP
Adjacent Angles
Definition: two angles in a plane that have a
common vertex and a common side but no
common interior points.
CAB and BAT are
adjacent angles.
C
B
CAT and BAT are
NOT adjacent
because they share
interior points.
A
T
Angle Bisector
Definition: a ray that divides an angle into
two congruent adjacent angles.
WY
Y
X
60
W
60
is an angle bisector.
XWY @YWZ
Z
Angle Addition Postulate
If B lies on the interior of AOC,
then mAOB + mBOC = mAOC.
mAOC = 115
B
A
50
O
65
C
C
B
mBQC = x - 7 mCQD = 2x - 1
mBQD = 2x + 34
Find x, mBQC, mCQD, mBQD.
Q
D
mBQC + mCQD = mBQD
x – 7 + 2x – 1 = 2x + 34
3x – 8 = 2x + 34
x – 8 = 34
x = 42
mBQC = 35
mCQD = 83
mBQD = 118
Update Postulate Section –
Angle Addition Postulate