1-2POINTS, LINES AND

PLANES

What is geometry?What did the acorn say after it grew up?

Gee, I’m a tree

Geo: metry:

Definition: A statement that explains the meaning of a word or phrase

Format for notes: (Optional method)

Term Definition Example

Earth Measure

Building BlocksUndefined terms

Point Most basic building block of geometry It has no size, only location Notation: Capital Letter

Line A straight, continuous arrangement of infinitely many

points Infinite length but no thickness Extends forever in two directions Notation: Naming any two points on line with line symbol

above Plane

Length and width but no thickness. Like a flat surface that extends infinitely along its length

and width. Notation: Script Capital Letter

AB

P

B

A

P

More Terms Collinear

On the same line Coplanar

On the same plane Line Segment (segment)

Two points called endpoints of the segment and all the points between them that are collinear with the two points.

Notation:

Length:

F

D

E P

Q

R

A

B

Endpoints

BAor AB

ABor AB m

5 cm

5AB

5AB

m

More Terms Congruent Segments

Two segments with the same lengths Symbol: Notation: Marking figures

Midpoint A point that divides the segment into

two congruent segments

A

B

C

D

CDABor CDABor CDAB mm

ON

M

NOMN

Midpoint

…aaaaand more…

RayA part of a line that begins at a point and extends infinitely in one direction.Notation:DA D

A

Opposite RaysTwo rays that share the same endpoint and form a line.Notation:

BC

A

CBCA and

Examples

B

D

C

A

M

L

K

N

4. Name a midpoint

5. Name congruent segments

1. Name a line

2. Name a line segment

3. Name a ray

F

A postulate or axiom is an accepted statement of fact.

Postulate 1-1Through any two points there is exactly one line.

Line t passes through points A and B. Line t is the only line that passes through both points. B

A

tPostulate 1-2If two distinct lines intersect, then they intersect in exactly one point.

AE DBand

intersect at point C.

B

ED

A

C

p.16: 9-49 odd, 53-59