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1.3 Collinearity, Betweenness, and Assumptions
Collinearity-
Definition- Points that lie on the same line are called collinear. Points that do not lie on the same line are called noncollinear.
Betweenness of Points- A point is between two points only if all the points are collinear.
Triangle Inequality-
For any three points:
1. They are collinear. they form a line.
2. They are noncollinear. They determine a triangle.
Assumptions from Diagrams-
How to Interpret a Diagram
You Should Assume:
Straight lines and angles
Collinearity of points
Betweenness of points
Relative positions of points
You Should Not Assume
Right angles
Congurent segments
Congurent angles
Relative sizes of segmemts and angles
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