1.2 angles
TRANSCRIPT
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1.2: Poolroom Math
Geometry Warm-up
If B is the midpoint of line AC and the coordinates of A are (-8, 0) and the coordinates of B are (-2, 6), find the coordinates of point C. 1.
2. pg. 46 # 44
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ANGLES
A Ray: part of a line, it has one endpoint and extends indefinitely in the other direction.
An Angle: the shape formed by two rays (sides of the angle) that start from one endpoint called the vertex.
A
B
C4
The angle is named by its vertex, by three points with the vertex in the middle, or by the number attached to the angle.
vertex
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Practice Problems
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How to Measure an Angle with a Protractor
STEP 1: Place the center of the protractor on the vertex of the angle.
STEP 2: Line up one of the sides of the angle with the 0 degree mark.
STEP 3: Find the measure of the angle by extending the other side. Remember: If the angle is obtuse, its measure will be > 90. If the angle is acute, its meaure will be < 90.
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Practice with Protractor:
Turn to page 40 Example B. Remember to follow the steps!
TIP: sometimes it helps if you turn the paper upside down to measure with the protractor!
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Why use the ≈ sign (approximately)?
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pg. 43 # 15 to 19
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Congruent Angles Remember the congruent sign (≅) when naming the angles!!!
Two angles are ≅ if they have tick marks OR the same measure (always degrees!)
38
38
Tick marks DO NOT go on the side!
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Congruent Angles....
Some angles are bisected and form 2 ≅ angles
Name 3 angles, 3 rays, 2 ≅ anglesWhy can't you name the angles in this problem by ONLY the vertex letter?
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Practice Naming Angles: pg. 41 Example C
What are 3 ways you KNOW that 2 angles are ≅ ?
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Using your Algebra to find angle measures!
90
42 64
23
26x
y
z
Every straight line = 180 (arrow to arrow)
The "box" means 90 ALWAYS!
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Now try pg. 42 # 1-37 odd
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