Warmup 1-3

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.

A

B

C

DE

F

G

HJ

Answers1. D, J, and H2. planes BCGF and CGHD3.4. 15. Sample: Planes AEHD and BFGC never intersect

HE

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

Lesson 1-3: Segments, Rays, Parallel Lines and Planes

Segment:

Ray:

Opposite Rays:

Segment AB, segment BA, or

AB, BA

Ray AB or AB (only way)

CA and CB or opposite

Rays have a sense of direction.

1

2

3

4

Draw three noncollinear points J, K, L.

Then draw JK, KL and L J.

SOLUTION

Draw J, K, and L

Draw JK.

Draw LJ.

K

LJDraw KL.

In-Class Example 1

Draw two intersecting lines. Label points on the

lines and name two pairs of opposite rays.

SOLUTION

XM and XN areopposite rays.

XP and XQ are opposite rays.

In-Class Example 2

Parallel:

Skew:

lm

Line l line m

These bars mean “is

parallel to”

l

m

Line l is skew to

line m

Example:Draw the figure below. Name all segments that areparallel to AE. Name all segments that are skew to AE

A B

CD

E F

G

Parallel segments: DH, BF, CG

Skew segments: BC, CD, FG, GH

In-Class Example 3

Assignment: Practice 1 – 3

Run in the same

direction.

Different direction – still don’t

touch.

H