# the radical rational…

## Hinged Mirrors & Polygons

on November 12, 2013

The last session I attended on Thursday afternoon at NCtM last week was with Erin Schneider from a
Louisville, KY.   Several hands-on and open ended tasks, sharing and talking.

The hinged mirrors were fun to play with and I wondered how I could use them in my classroom.

The hinge is placed either off the edge of a sheet of paper or on the edge of a paper.

Convince me its a square.

How can you create a rhombus that is not a square.

What happens as the central angle gets smaller? Larger?
For my students, I feel this allows them to really see a polygon diseected into several triangles from the central angle.

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### 2 responses to “Hinged Mirrors & Polygons”

1. This seems like it could be really interesting. You could certainly make some convincing arguments about lengths based on the idea of reflections being the same distance “behind” the mirror as in front of it. Though, I wonder, is this something that gets obscured by the fact that there are multiple reflections?

2. Brianne says:

I saw this at a conference I went to last spring. We also had a 360 degree protractor that was printed on a transparency. We laid the protractor on top of the mirrors and were able to see the interior angle measure of the regular polygons.