1-2 points, lines and planes
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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
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