9.3 Classifying Angles

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9.3 Classifying Angles
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Angle Classification
Angles are classified by their measure.
Right angle -- An angle whose measure is exactly
90.
Indicates a right angle
Acute angle An angle whose measure is less than
90.
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Angle Classification Cont.
Obtuse Angle An angle whose measure is between
90 and 180.
Straight Angle An angle whose measure is
exactly 180.
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Now You Try!
Classify the angle as acute, right, obtuse, or
straight.
right
acute
straight
obtuse
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Using Vertical Angles
Vertical angles When two lines that intersect,
the angles opposite each other are called
vertical. Vertical angles have equal measures
(congruent).
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2
4
3
/ 1 and / 3 are vertical angles.
/ 2 and / 4 are vertical angles.
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Complementary and Supplementary Angles
Complementary Angles Two angles are
complementary if the sum of their angles is 90.
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/ 1 / 2 90.
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Remember this saying if you have trouble
remembering the difference You have the right
to compliment someone
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Complementary and Supplementary Angles Cont.
Supplementary Angles Two angles are
supplementary if the sum of their angles is 180.
/ 3 / 4 180
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4
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Your Turn!
Tell which angles are vertical.
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/ 1 / 3
1
3
4
/ 2 / 4
If / 1 measures 40, what is the measure of all
the other angles?
/ 3 is 40 because it is congruent
/ 2 / 4 is 140
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Your Turn Cont.
Tell whether the angles are complementary or
supplementary.
40
48
132
50
supplementary
complementary
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Your Turn Continued
C
B
A
D
F
30
E
Name a pair of vertical angles.
/ EFD and / AFB
/ AFB and / AFC
Name a pair of complementary angles.
Name a pair of supplementary angles.
/ BFC and / CFE