Section 1.4Section 1.4

Segments, Rays, Parallel Segments, Rays, Parallel Lines, and PlanesLines, and Planes

1-4 Segments, Rays, 1-4 Segments, Rays, Parallel Lines, and PlanesParallel Lines, and Planes

Objectives / “I can…”Objectives / “I can…” Define line segments and raysDefine line segments and rays Properly name line segments and Properly name line segments and

raysrays Identify parallel lines and skew linesIdentify parallel lines and skew lines

Line SegmentLine Segment• is part of a line that has a beginning and an end (called endpoints).

• named using both endpoints and w/ a little segment on top

A BAB or BA

Ch 1-4: Segments, Rays, Ch 1-4: Segments, Rays, Parallel Lines & PlanesParallel Lines & Planes

RayRay• Is part of a line that has a specific starting point and goes forever in one direction.

• Name a ray starting with the endpoint. (The 2nd letter tells which direction to

go.)

• Put a small ray symbol over the letters.

D E F

DE or

DF

Rays, continuedRays, continued

Are these two rays the same?Are these two rays the same?

A

B

A

B

No• Different endpoints• Extend in different directions

BA

AB

Opposite RaysOpposite Rays• are 2 collinear rays with the same endpoint.

• they form a line

R O B I N

BR & BN are opp. rays

Parallel LinesParallel Lines ~ ~ coplanar lines that do coplanar lines that do not intersectnot intersect

Skew LinesSkew Lines ~ ~ noncoplanar noncoplanar They are not parallel They are not parallel & they do not intersect& they do not intersect

Same direction

&Same plane

Different direction

&Different

plane

Lines that do not intersect Lines that do not intersect

may or may not be coplanar.may or may not be coplanar.

Hint: Parallel lines – same direction same plane

Skew Lines – different direction different plane

Parallel to GJ?Skew to GJ?

HI, DNAB, CD, CH

Parallel PlanesParallel Planes

Parallel planes are planes that never Parallel planes are planes that never intersectintersect Example: the purple planes in the above Example: the purple planes in the above

illustrationillustration A line and plane that never intersect A line and plane that never intersect

are also parallelare also parallel

Quick CheckQuick Check