Lesson:
Tris and Untris 


Part 1 
Making Triangles Below are 12 line segments (or straws) of various length. Make as many unique triangles as you can using these segments. Use this Sketchpad file to help you. After you make your triangles, record them in the table below.
Part 2  Making “Untriangles” We know that a triangle has three sides that form a closed shape. But what’s an "untriangle?" Below is an example of an untriangle. Why do you think it's called an untriangle? Make and record your untriangles below:
Below are candidates for “trianglehood.” Indicate which are triangles and which are “wannabe” triangles (untriangles).
Some Questions: 1. If two of the line segments are equal, will you always be able to make a triangle with the third stick? Explain.
4.
Explain when it is NOT possible for you to make a
triangle with three segments.
Source: Original Version
1.0 developed at CIESE
Center for Innovation in Engineering & Science Education (2007) Revised 11.13.19 currently under construction
