Parallel and Perpendicular Lines

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# Parallel and Perpendicular Lines - PowerPoint PPT Presentation

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.

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Presentation Transcript

### Parallel and Perpendicular Lines

Lines & Angles

Section 3-1

Lines & Angles
• Parallel Lines (ll) - are coplanar and do not intersect.
• Perpendicular Lines (⏊) – intersect at 90ํangles.
• 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**
Examples:

What are some examples of perpendicular lines??

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:
• Alternate Exterior Angles:
Name ‘em:
• Corresponding Angles:
• Same-side: