Unit 1 Day 1

1. Unit 1 – Foundation of Geometry
Day 1

2.  Point – indicates a location and has no size
A (Point A)
 Line – represented by a straight path that
extends in 2 opposite directions without end
and has no thickness. A line contains
infinitely many points.
l (Line AB, line BA,
or line l)
B
A
 Collinear – points that lie on the same line

3.  Plane – represented by a flat surface that
extends without end and has no thickness. A
plane contains infinitely many lines.
P (Plane ABC or
A plane P)
B C
 Coplanar – points that lie on the same plane

5.  Segment – part of a line that consists of 2
endpoints and all points between them
(segment EF or
E F segment FE)
 Ray – part of a line that consists of 1
endpoint and all the points of the line on one
side of the endpoint
B (ray AB,
A not ray BA)
 Opposite rays – 2 rays that share the same
endpoint and form a line

6. D E F
1. Name 3 segments.
2. Name 6 rays.
3. Name 2 opposite rays.

7. Postulate – an accepted statement of fact
 Through any 2 points there is exactly 1 line.
 If 2 distinct lines intersect, then they
intersect in exactly 1 point.
 If 2 distinct planes intersect, then they
intersect in exactly 1 line.
 Through any three noncollinear points there
is exactly 1 plane.

8.  Parallel lines – coplanar lines that never
intersect (symbol  II )
 Parallel planes – planes that never intersect
 Perpendicular lines – lines that intersect and
form right angles (symbol  ⊥ )
 Perpendicular planes – planes that intersect
to form right angles
 Skew lines – noncoplanar lines that never
intersect

9. 1. Name a pair of II segments and a pair of II planes.
2. Name a pair of ⊥ segments and a pair of ⊥ planes.
3. Name 2 pairs of skew segments.
4. Are 퐵퐶 and 퐸퐻 coplanar? Explain.