1. Warmup 1-3 Use the diagram above. 1. Name three collinear points.F C G A
Use the diagram above.
1. Name three collinear points.
2. Name two different planes that contain points C and G.
3. Name the intersection of plane AED and plane HEG.
4. How many planes contain the points A, F, and H?
5. Show that this conjecture is false by finding one counterexample:
Two planes always intersect in exactly one line. E D H J

2. 5. Sample: Planes AEHD and BFGC never intersect
Answers
1. D, J, and H
2. planes BCGF and CGHD 3.
4. 1
5. Sample: Planes AEHD and BFGC never intersect HE

3. Lesson 1-3: Segments, Rays, Parallel Lines and Planes
Term
Own Words
Definition
Segment
Ray
Opposite rays
Parallel lines
Skew lines
Parallel Planes
Part of a line with 2 endpoints and all points in between
Part of a line with 1 endpoint and all points in one direction
Two rays that share the same endpoint. They form a line.
Coplanar lines that do not intersect.
Non-coplanar lines and do not intersect (not parallel)
Planes that do not intersect

4. Rays have a sense of direction.
Segment:
Ray:
Opposite Rays:
Segment AB, segment BA, or
AB, BA
Ray AB or AB (only way)
Rays have a sense of direction.
CA and CB or opposite

5. In-Class Example 1
Draw three noncollinear points J, K, L. Then draw JK, KL and L J.
SOLUTION K L J
Draw J, K, and L 1 2
Draw JK. 3
Draw KL. 4
Draw LJ.

6. XP and XQ are opposite rays.
In-Class Example 2
Draw two intersecting lines. Label points on the lines and name two pairs of opposite rays.
SOLUTION
XM and XN are
opposite rays.
XP and XQ are opposite rays.

7. These bars mean “is parallel to”
Skew:
Line l line m l
These bars mean “is parallel to” m l
Line l is skew to line m m

8. Draw the figure below. Name all segments that are
In-Class Example 3
Example:
Draw the figure below. Name all segments that are
parallel to AE. Name all segments that are skew to AE D C A B H
Run in the same direction. G E F
Parallel segments: DH, BF, CG
Skew segments: BC, CD, FG, GH
Different direction – still don’t touch.
Assignment: Practice 1 – 3