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Section 1-1, 1-3
Symbols and Labeling
Vocabulary
• Geometry
–Study of the set of points
• Space
–Set of all points
• Collinear
–Points that lie on the same line
• Non-collinear
–Points that do not lie on the same
line
Vocabulary Continued
• Coplanar
–Points that lie on the same plane
• Non-coplanar
–Points that do not lie on the same
plane
• Postulate
–Statement accepted without proof
Point
• No size
• Simplest figure in geometry
• Named by
–A capital letter
• Represented by a small dot
• Indicates a definite location
Line
• Series of points
• Extends in two opposite directions
without end
• Name by
–Two points on the line
–Single lower case letter
• Has no thickness
• Is straight
• Can not be measured
Plane
• Flat surface
• Extends in all directions without
end
• No thickness
• Named by
–Single capital letter
–Three non-collinear points on
the plane
• Non-collinear
–Points not on the same line
Segment
•
•
•
•
Is part of a line
Has two endpoints
Can be measured
Named by
–Two endpoints
Ray
• Is part of line
• Has only one endpoint
• Extends in one direction without
end
• Named by
–The endpoint and any point on
the ray
• Can not be measured
Opposite Rays
• Two rays that share a common
endpoint and extend in opposite
directions.
• They form a line
Parallel Lines
• Coplanar lines that do not intersect
• Segments and rays are parallel, if
the lines that contain them are
parallel
A
B
C
D
Skew Lines
• Lines that are in different planes
• They are neither parallel nor
intersecting
Parallel Planes
• Planes that do not intersect
• Examples in this room
–Plane of the floor and plane of
ceiling
–Horizontal planes never intersect
–Vertical planes can intersect
Section 1-2
Angles
• Go to angles
1.1 postulates
• Postulate 1
– Two points determine one line
• Postulate 2
– Three non-collinear points determine
exactly one plane
1-3 Postulates
• Postulate 3
– If two lines intersect, then their
intersection is a point
• Postulate 4
– If two planes intersect, then their
intersection is a line