# Chapter 4 1 Skew Parallel and Perpendicular Lines

• Slides: 19

Chapter 4. 1 Skew, Parallel and Perpendicular Lines

Objectives: We’ll learn… • Define the characteristics of skew, parallel and perpendicular lines.

Skew Lines Skew lines lie in different planes. They are • Not parallel • Not intersecting • Not perpendicular.

Skew lines are noncoplanar lines. (Noncoplanar lines cannot intersect. )

SKEW LINES • Lines that lie in different planes. They are neither parallel nor intersecting.

SKEW LINES • Lines that lie in different planes. They are neither parallel nor intersecting. G B F A H E D C CD and FA are SKEW LINES FA and BD are SKEW LINES

Use the figure to find the following: A E B F D H Two pairs of Parallel Lines C G Two pairs of Parallel Planes Two pairs of Skew Lines

28 PARALLEL LINES • Def: lines that do not intersect; must be coplanar. B • Illustration: A l C m • Notation: D l || m AB || CD p. 129

Two lines are parallel if they do not intersect. A B C D Read as line AB is parallel to line CD. EX 1: Are the lines parallel?

Examples of Parallel Lines • • • Hardwood Floor Opposite sides of windows, desks, etc. Parking slots in parking lot Parallel Parking Streets: Laramie & Le. Claire

Examples of Parallel Lines • Streets: Belmont & School

PERPENDICULAR LINES 29 • Def: Lines that intersect to form a right angle. m • Illustration: n • Notation: m n • Key Fact: 4 right angles are formed. p. 79

PERPENDICULAR • Lines that intersect to form right angles. 90° 90°

When two lines intersect at right angles, TRICK: 4 right angles are formed, but it shows 1 only. (The other 3 are invisible. ) They are called perpendicular lines. ┴

Ex. of Perpendicular Lines • Window panes • Streets: Belmont and Cicero

Language of Geometry

Parallel lines & Transversal

Angles, Parallel Lines & Transversal

Homework p. 144, 1 -9, 15 -17