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Time Estimate	Activity	Main Idea
15 min (2:45)	Does this work for concave non-regular polygons? Partition the polygons into the minimum number of triangles.	Justification for the concave non-regular polygon interior angle sums.

Step-by-step guide:

1. Have participants draw concave polygons and measure the angles, similar to the previous situation.

Drawing the triangles in the concave polygons may be a bit tricky. Have the participants label the triangles as they make them. Internet Sources:

https://mste.illinois.edu/m2t2/algebra/regs.gsp is a Geometer's Sketchpad file of regular polygons. Resources for this unit are available at https://mste.illinois.edu/m2t2/algebra/