Parallel Lines and Transversals

1
Parallel Lines and Transversals
2
Parallel Lines

• Two lines in the same plane that never intersect
  are parallel.
• Examples
• Railroad tracks
• Rows in a field

3
Parallel Lines

• The symbol ll means is parallel to.
• The red arrows used in diagrams indicate the
  lines are parallel.
• In the figure BC ll AD.

4
Skew Lines

• Two lines that do not intersect and are not in
  the same plane are skew lines.

5
Transversal

• A line that intersects two or more coplanar lines
  is called a transversal.
• The lines the transversal intersects dont have
  to be parallel.

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Transversals

• When a transversal intersects two lines, eight
  angles are formed.
• These angles are given special names
• Exterior angles
• Interior angles
• Consecutive interior or same-side interior angles
• Alternate exterior angles
• Alternate interior angles
• Corresponding angles

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Transversals

• Exterior angles
• ?1, ?2, ?7, ?8
• Interior angle
• ?3, ?4, ?5, ?6

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Transversals

• Consecutive interior or same-side interior angles
• ?3 and ?5, ?4 and ?6
• Alternate exterior angles
• ?1 and ?8, ?2 and ?7
• Alternate interior angles
• ?3 and ?6, ?4 and ?5
• Corresponding angles
• ?1 and ?5, ?2 and ?6, ?3and ?7, ?4 and ?8

9
State the transversal that forms each pair of
angles. Then identify the special name for the
angle pair.

• ?6 and?7
• ?16 and ?2
• ?13 and ?5
• ?8 and ?10
• ?11 and ?15
• ?4 and ?8