Download 3-1 Properties of Parallel Lines M11.B 2.3.11.A

3-1 Properties of Parallel Lines
M11.B
2.3.11.A
Objectives:
1) To identify angles formed by two lines and a
transversal
2) To prove and use properties of parallel lines
Vocabulary
 A transversal is a line that intersects two coplanar lines at
two distinct points. (8 angles are formed)
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4 Types of Angles
1)
Alternate interior angles
2)
Same-side interior angles
3)
4)
Corresponding angles
Alternate exterior angles
5 6
1 3
4 2
7 8
Example: Identifying Angles
1)
Same side Interior Angles
2)
Corresponding Angles
4 1
3 2
8 5
7 6
Postulate 3-1: Corresponding Angles
 If a transversal intersects two parallel lines, then
corresponding angles are congruent.
Example:
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Alternate Interior/Exterior Angles
 If a transversal intersects two parallel lines, then alternate
interior angles and the alternate exterior angles are
congruent.
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Same Side Interior Angles
 If a transversal intersects two parallel lines, then same-side
interior angles are supplementary.
Example:
Find the measure of each missing angle…Justify your answer
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Vocabulary - Review
 Straight Angle – Angle(s) measure 180° to form a straight
angle.
Example: Using algebra to find Angle Measures
2x
y
(y - 50)