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ANGLES, ANGLES, ANGLES
Naming Angles
Measuring Angles
Classifying Angles
The Angle Addition Postulate
An angle is formed by two rays with a common
endpoint called a vertex.
CD and CE are the rays
that form the sides of the
angle. C is the common
endpoint, or vertex.
C - vertex
D
E
There are four different ways to name an angle:
#1:
-by its vertex with  in front of the capital
letter
D
C
This is  C.
E
There are four different ways to name an angle:
#2:
-by a number placed inside the angle with
 in front of the number
This is  3.
D
3
C
E
There are four different ways to name an angle:
#3:
-by three letters - a point on one of the rays
followed by the vertex of the angle followed by a
point on the other ray with  in front the three
capital letters.
This is  DCE
or  ECD.
D
C
E
There are four different ways to name an angle:
#4:
-by a lower case letter placed inside the
angle with  in front of the lower
case letter.
This is  a.
D
a
C
E
Click on the correct name for the angle shown.
D
E
TEJ
d
T
J
JTE
etj
Think about capital letters and lower case letters.
Think about what the middle letter should be.
WHITE NOTE CARD:
ANGLES
Formed by two rays with a common endpoint called a vertex.
BC and BG are the rays, B is the vertex
Named by:
- the vertex (a capital letter)
B
- a number placed inside the angle 8
- three capital letters - a point on one ray
followed by the vertex followed by a point
CBG
on the other ray; vertex always in the middle GBC
- a lower case letter placed in side the angle
All of these start with .
C
8
B
G
Angles are measured in degrees using a
protractor. The protractor is used to
measure the opening between the two rays
that make up the angle.
Angles can be classified in four different ways:
Acute angles - angles that measure less than 90º
Right angles - angles that measure 90º
Obtuse angles - angles that have a measure greater than
90º but less than 180º
Straight angles - angles that measure 180º
True or False - Click true or false
next to each statement.
TRUE
/
FALSE
- All right angles are congruent.
TRUE
/
FALSE
- All obtuse angles are congruent.
TRUE
/
FALSE
- An obtuse angle and an acute
angle could be congruent.
TRUE
/
FALSE
- Three acute angles could be
congruent.
Continue – all finished with the True / False questions.
WHITE NOTE CARD:
ANGLE CLASSIFICATION
Angles can be classified in four different ways:
Acute angles - angles that measure less than 90º
Right angles - angles that measure 90º
Obtuse angles - angles that have a measure greater than
90º but less than 180º
Straight angles - angles that measure 180º
If R is in the interior of PQS, then
m PQR + m RQS = m PQS.
P
Q
R
S
If R is in the interior of PQS, then
m PQR + m RQS = m PQS.
So, if R is in the interior of the
big angle, then the sum of the
measures of the two smaller
angles will equal that big angle.
P
Q
R
S
If R is NOT in the interior of PQS, then
m PQR + m RQS  m PQS.
R
P
Q
S
If m PQR + m RQS = m PQS,
then R is in the interior of PQS.
What does this mean? Think about the
second part of the
Segment Addition Postulate.
COLORED NOTE CARD
ANGLE ADDITION POSTULATE
If R is in the interior of PQS, then
m PQR + m RQS = m PQS.
P
Q
If m PQR + m RQS = m PQS, then
R is in the interior of PQS.
R
S