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Parallel and Perpendicular Lines. Lines & Angles Section 3-1. Lines & Angles. Parallel Lines ( ll ) - are coplanar and do not intersect. Perpendicular Lines (⏊) – intersect at 90 ํ angles . Skew Lines – are not coplanar. Skew lines are not parallel and do not intersect. - PowerPoint PPT Presentation
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Parallel and Perpendicular Lines
Lines & AnglesSection 3-1
Lines & Angles• Parallel Lines (ll) - are coplanar and do not intersect.
• Perpendicular Lines ( ) – intersect at 90⏊ ํ angles.
• Skew Lines – are not coplanar. Skew lines are not parallel and do not intersect.
• Parallel Planes – are planes that do not intersect.
• **See diagram on pg. 146 for examples**
What are some examples of perpendicular lines??
Examples:
Angle Pairs formed by a Transversal• Transversal – a line that intersects two coplanar lines at two different points.
The transversal t and the other two lines r and s for eight angles.
• Corresponding angles – lie on the same side of the transversal t, on the same sides of lines r and s. ( 1 & 5)∠ ∠
• Alternate interior angles – nonadjacent angles that lie on opposite sides of the transversal t, between lines r and s. ( 3 & 5)∠ ∠
• Alternate exterior angles – lie on opposite sides of the transversal t, outside lines r and s. ( 2 & 8)∠ ∠
• Same-side interior angles – lie on the same side of the transversal t, between lines r and s. ( 3 & 6)∠ ∠
Angles formed by parallel lines & transversals
Section 3-2
Corresponding Angles Postulate• If two parallel lines are cut by a transversal, then the pairs of corresponding
angles are congruent.
• Name the pairs of corresponding angles.
Alternate Interior Angles Theorem• If two parallel lines are cut by a transversal, then the pairs of alternate interior
angles are congruent.
• What are the alt. int. angles?
Alternate Exterior Angles Theorem• If two parallel lines are cut by a transversal, then the two pairs of alternate
exterior angles are congruent.
• Exterior angles (using correct lingo on how to name an angle)??
Same-Side Interior Angles Theorem• If two parallel lines are cut by a transversal, then the two pairs of same-side
interior angles are supplementary.
• Example???
Name ‘em:• Alternate Interior Angles:
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• Alternate Exterior Angles:
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Name ‘em:• Corresponding Angles:
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• Same-side:
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