3.1

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3.1 Identify Pairs of Lines and Angles

• Parallel Lines two lines are parallel if they
  do not intersect AND are coplanar
• Skew Lines Two lines are skew lines if they do
  not intersect and ARE NOT coplanar.
• Parallel Planes Two planes are parallel if they
  do NOT intersect.

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3.1 Identify Pairs of Lines and Angles
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3.1 Identify Pairs of Lines and Angles

• Example 1
• Think of each segment in the figure as part of a
  line. Which line(s) or plane(s) in the figure
  appear to fit the description?
• Line(s) // to Line CD and
• containing point A
• Line(s) skew to Line CD and
• containing point A.

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3.1 Identify Pairs of Lines and Angles

• Example 1
• Think of each segment in the figure as part of a
  line. Which line(s) or plane(s) in the figure
  appear to fit the description?
• Line(s) perpendicular to Line CD
• and containing point A.
• Plane(s) parallel to plane EFG
• and containing point A.

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3.1 Identify Pairs of Lines and Angles

• PARALLEL AND PERPENDICULAR LINES
• Through a point not on a line,
• there are infinitely many lines.
• Exactly one parallel.
• Exactly one perpendicular.

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3.1 Identify Pairs of Lines and Angles
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3.1 Identify Pairs of Lines and Angles

• Example 2
• The figure shows a swing set on a playground.
• Name a pair of perpendicular lines.
• Name a pair of parallel line.
• Is Line DH perp to Line LM? Explain?

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3.1 Identify Pairs of Lines and Angles

• A transversal is a line that intersects two or
  more coplanar lines at different points.

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3.1 Identify Pairs of Lines and Angles

• Example 3
• Identify all pairs of angles of the given type.
• Corresponding
• Alternate Interior
• Alternate Exterior
• Consecutive Interior

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3.1 Identify Pairs of Lines and Angles

• Example 4
• Classify the pair of numbered angles.
• a. b.
• c.