ANGLES, ANGLES, ANGLES

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ANGLES, ANGLES, ANGLES

• Naming Angles
• Measuring Angles
• Classifying Angles
• The Angle Addition Postulate

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What is an angle?
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.
D
C - vertex
E
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NAMING ANGLES
There are four different ways to name an angle
1 -by its vertex with ? in front of the
capital letter
D
This is ? C.
C
E
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NAMING ANGLES
There are four different ways to name an angle
2 -by a number placed inside the angle
with ? in front of the number
D
This is ? 3.
3
C
E
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NAMING ANGLES
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
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NAMING ANGLES
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
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NAMING ANGLES
Click on the correct name for the angle shown.
?D
E
?TEJ
d
T
?JTE
J
?etj
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SUPER
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Try Again!
Think about capital letters and lower case
letters. Think about what the middle letter
should be.
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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
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ANGLE MEASURE
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.
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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
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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.
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CORRECT!!!
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NO - READ THE STATEMENT AGAIN.
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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
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ANGLE ADDITION POSTULATE
If R is in the interior of ?PQS, then m? PQR
m? RQS m? PQS.
P
R
S
Q
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ANGLE ADDITION POSTULATE
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
R
S
Q
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ANGLE ADDITION POSTULATE
If R is NOT in the interior of ?PQS, then m? PQR
m? RQS ? m? PQS.
R
P
S
Q
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ANGLE ADDITION POSTULATE
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.
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COLORED NOTE CARD
ANGLE ADDITION POSTULATE If R is in the interior
of ?PQS, then m? PQR m? RQS m?
PQS. If m? PQR m? RQS m? PQS, then R
is in the interior of ?PQS.
R
P
S
Q
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HOMEWORK / CLASSWORK