Download Lesson 1.4: Measure and Classify Angles

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Transcript 
Lesson 1.4: Measure and
Classify Angles
• An angle consists of two different rays with the
same endpoint.
• The rays are the sides of the angle.
• The endpoint is the vertex of the angle.
Ex. 1: Write 3 names for the angle shown. Then
name the vertex and sides of the angle.
A
B
C
Ex.2: Name the three angles in the diagram.
Classifying Angles:
Angles can be classified as acute, right,
obtuse, and straight.
• Acute angles have a measure greater than 0
and less than 90.
• Right angles have a measure of 90.
• Obtuse angles have a measure greater than
90 and less than 180.
• Straight angles have a measure of 180.
Measuring Angles:
• A protractor can be used to approximate the
measure of an angle.
• An angle is measured in units called degrees
(o).
Postulate 3 Protractor Postulate:
The measure of AOB is equal to the absolute
value of the difference between the real
numbers for OA and OB .
A
O
B
EXAMPLE 3
Measure and classify angles
Use the diagram to find the measure of the indicated angle. Then classify the
angle.
a. <GHL
b. <JHK
b. <GHK
c. <GHJ
Postulate 4 Angle Addition Postulate:
If P is in the interior of RST , then
mRST  mRSP  mPST
Ex 4 and 5: Find the indicated angle
measure.
Q
R
B
76°
51°
26°
S
T
m < QST = _____
A
C
D
m < QST = _____
Ex.6: Given that mLKN  145o , find mLKM
and mMKN
.
Ex.7: Given that KLM is a straight angle,
find mKLN and mNLM .
Ex.8: Given that EFG is a right angle, find
mEFH and mHFG .
Congruent Angles:
Two angles are congruent angles if they have
the same measure.
Ex.9: Use the diagram below.
a. Identify all pairs of congruent angles.
o
o
m

PQR

130
m

QRS

84
b. Given that
,
,and
mTSR  121o
Find the other angle measures in the diagram.
Ex 10: Find the indicated angle measure.
1. a°
2. b°
3. c°
4. d°
c°
d°
e°
a°
103° b°
f°
48°
5. e°
6. f°
An angle bisector is a ray that divides an angle
into two angles that are congruent.
Ex.11: In the diagram below, YW bisects XYZ ,
0
m

XYW

18
and
. Find the other two angle
measures not given.
.
In the diagram BD bisects <ABC.
Find m < ABC.
D
A
(5x-11)°
B
(4x+1)°
C
Homework
Pgs 28-30 #1, 3-10, 15-31, 33-38, 40-42
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