1. Unit 1 Overview Video
Please Press Play for a summary
of the material in Unit 1.
2. Vocabulary
Euclidean Geometry is based on the definitions and the undefined terms point, line and plane.
Point – Name a point with a letter. Example: Point A
Line – Name a line with letter or with symbols. Example: Line m or PQ
Plane – Name a plane with 1, 3, or 4 letters: Example: Plane H or Plane JKL or Plane JKLM
Other figures:
Ray – Name a ray with symbols and letters (from the endpoint to the arrow). Example: PQ
Segment – Name a segment with symbols and letters : PQ
Angle – Name an angle with one or three letters: / P or / NPQ
A
P
Q
P
Q
P
Q
P
Q
N
3. Vocabulary
Collinear Points are all the points that lie on the same line. Since it only takes two points to
define a line, any two points are collinear.
Noncollinear points are points that do NOT line on the same line.
Coplanar Points are all the points that lie on the same plane. Since it only takes three
points to define a plane, any three or more points are coplanar.
Noncoplanar points are points that do NOT lie on the same plane.
P
Q
P
Q
P
Q
P
Q
M M
P
Q
M
P
Q
M
P
Q
M
P
Q
M
B B
9. Postulates
Postulate 1: Through any two points, there is exactly one line.
Postulate 2: Through any three points not on the same line, there is exactly one plane.
Postulate 3: A line contains at least two points.
Postulate 4: A plan contains at least 3 points not on the same line.
Postulate 5: If two points lie in a plane, then the entire line containing those points lies in that plane.
Postulate 6: If two lines intersect, then their intersection is exactly one point.
Postulate 7: If two planes intersect, then their intersection is a line.
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