1. Segments, Rays, Parallel Lines, and Planes
Section 1.4
Segments, Rays, Parallel Lines, and Planes

2. 1-4 Segments, Rays, Parallel Lines, and Planes
Objectives / “I can…”
Define line segments and rays
Properly name line segments and rays
Identify parallel lines and skew lines

3. Ch 1-4: Segments, Rays, Parallel Lines & Planes
Line 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
AB or BA
A B

4. Ray
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.
DE or
D E F DF

5. Rays, continued Are these two rays the same? B AB A B A BA No
Different endpoints
Extend in different directions

6. Opposite Rays are 2 collinear rays with the same endpoint.
they form a line
R O B I N
BR & BN are opp. rays

7. Parallel Lines ~ coplanar lines that do
Lines that do not intersect
may or may not be coplanar.
Parallel Lines ~ coplanar lines that do
not intersect
Skew Lines ~
noncoplanar They are not parallel
& they do not intersect
Same direction &
Same plane
Different direction &
Different plane

8. Hint: Parallel lines – same direction
same plane
Skew Lines – different direction
different plane

9. Parallel to GJ?
Skew to GJ?
HI, DN
AB, CD, CH

10. Parallel Planes Parallel planes are planes that never intersect
Example: the purple planes in the above illustration
A line and plane that never intersect are also parallel

11. Quick Check