3.1 Relationships between lines

Vocabulary Parallel Lines- two lines that lie in the same plane and do not intersect Illustration: Notation: l ||m AB || CD A B C D l m

Examples of parallel lines Hardwood Floor Opposite sides of windows, desks, etc. Parking slots in parking lot

Vocabulary Perpendicular- two lines who are in the same plane that intersect at a 90° angle Illustration: Notation: m  n m n

Examples of perpendicular lines Streets: Franklin Ave and Centre Street

Vocabulary Skew Lines- Two lines who are in different planes and never intersect. Skew lines are NOT parallel. Illustration- Notation: AE and CD are skew

Examples of skew lines

Skew lines continued Are the following lines skew…? No, they are || 1. AE and FB? No, they are || 2. FB and CG? No, they are || 3. AE and BD? Yes, they are skew

Vocabulary Parallel Planes- planes that do not intersect Plane AEB || Plane CGH

Example 1 Fill in the blank with ∥ or ⊥ ⊥ ∥ ⊥ ∥

Example 2 Identify each of the following a. a pair of parallel segments BF || EJ b. a pair of skew segments BF and DE are skew. c. a pair of perpendicular segments BF  FJ d. a pair of parallel planes plane FJH || plane BCD

Example 3 Identify each of the following I. a pair of parallel segments EH || FG J. a pair of skew segments BF and EH K. a pair of perpendicular segments CG  GH L. a pair of parallel planes Plane ABC || Plane EFG