1.2 Points, Lines, and PlanesUnit 1, Day 1

Do Now

Match the word with its informal definition. (Copy in your notes.)

1. Extends infinitely in one dimension.

2. Has no dimension.3. Extends infinitely in

two dimensions

A. Point

B. Plane

C. Line

More Vocabulary

Points are said to be collinear if they lie __________________________

Points are said to be coplanar if they lie _________________________

Let’s think…

You can draw a line through any _____ points. So in order to name noncollinear points, you need at least ________.

You can draw a plane through any ______ points. So in order to name noncoplanar points, you need at least ________.

Ex. 1: Naming Collinear and Coplanar Points

a. Name three points that are collinear.

b. Name four points that are coplanar.

c. Name three points that are noncolinear.

G

D E F

H

More Vocabulary

The line segment AB ( _____) consists of the endpoints ___ and ____ and all of the points on line AB that are _______________.

The ray AB (______) consists of the initial point ___ and all of the points on line AB that are on the same side as point ____. Ray AB and ray BA are not the same!

More Vocabulary

If C is between A and B, then ray CA and ray CB are considered ___________________. Note: When we say “between” in this class, it

implies that the three points are on the same line.

Ex. 2: Drawing lines, segments and rays

Draw three noncollinear points, J, K, and L.

Then draw JK, KL and LJ.

Ex. 3: Drawing Opposite Rays

Draw two lines, MN and PQ, that intersect at a point, X. Name two pairs of opposite rays.

Intersection

Two or more geometric figures are said to intersect if _______________________________. The intersection is the set of points the figures

have in common (usually another figure!).

Line with plane:

Plane with another plane:

Closure

Suppose rays CA and AT are opposite rays. What does this tell you about the points C, A, and T?