you are here > Class Notes - Chapter 1 - Lesson 1-3

Printable version

Collinearity, Between, and Assumptions - Lesson 1-3

Today, we began by covering the concept of collinear and noncollinear points.  We also talked about what it meant for a point to be between two other points.


We then discussed the fact that there are only two possibilities given three that determines a triangle and one that doesn't.  This should allow you to determine a range of values for the length of third side of a triangle given the length of the other two:

Triangle Inequality

We then discussed the things we could assume from a diagram and those we couldn't:


...and then worked through this example:

Example of assumptions

Other Links
Class Notes
Lesson 1-1
Lesson 1-2
Lesson 1-3
Lesson 1-4
Lesson 1-5
Lesson 1-6
Lesson 1-7
Lesson 1-8
Lesson 1-9
Test Topics
If you have questions, email me at