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Lesson 1: Angles and Angle Classification
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Angles A shape formed by two rays sharing a common endpoint; contains two rays and a vertex vertex—point common to two rays of a triangle or two sides of a polygon ray vertex ray—has one endpoint and goes infinitely in one direction
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Naming Angles An angle is named by three letters. The vertex must be in center. A 1 B C
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Types of Angles Acute angle: An angle whose measure is greater than zero degrees and less than 90 degrees Which angles are not acute? 1 2 3 4 5
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Types of Angles Right angle: Angle that measures 90 degrees
Which angle is a right angle? 1 2 3 4 5
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Types of Angles Obtuse angle: One angle measures greater than 90 degrees and less than 180 degrees Which angle is an obtuse angle? 1 2 3 4 5
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This is a ray. It only goes in one direction.
Straight Angle Straight angle: A line that goes infinitely in both directions and measures 180 degrees Which is not a straight angle? 2 1 This is a ray. It only goes in one direction.
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Adjacent angles are “side by side” and share a common ray.
15º 45º
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These are examples of adjacent angles.
45º 80º 35º 55º 130º 50º 85º 20º
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These angles are NOT adjacent.
100º 50º 35º 35º 55º 45º
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When 2 lines intersect, they make vertical angles.
75º 105º 105º 75º
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Vertical angles are opposite one another.
75º 105º 105º 75º
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Vertical angles are opposite one another.
75º 105º 105º 75º
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Vertical angles are congruent (equal).
150º 30º 150º 30º
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Supplementary angles add up to 180º.
40º 120º 60º 140º Adjacent and Supplementary Angles Supplementary Angles but not Adjacent
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Complementary angles add up to 90º.
30º 40º 50º 60º Adjacent and Complementary Angles Complementary Angles but not Adjacent
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Practice Time!
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Directions: Identify each pair of angles as vertical, supplementary, complementary, or none of the above.
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#1 120º 60º
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#1 120º 60º Supplementary Angles
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#2 75º 75º
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#2 Vertical Angles 75º 75º
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#3 25º 65º
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#3 25º 65º Complementary Angles
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Directions: Determine the missing angle.
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#1 ? 45º
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#1 135º 45º
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#2 ? 65º
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#2 25º 65º
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#3 ? 35º
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#3 35º 35º
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#4 ? 50º
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#4 130º 50º
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