There are many many different types of polygons. Today we are going to work with many types of flat polygons. We are going to start out with building a triangle. I would like for you to build one triangle for me. In two previous lessons we already learned something about the triangle we have already built today. (See geometry-triangles and geometry-right triangles). Please explain what you recall about the triangle that you’ve built. How do we know this is accurate and certain?
Please make a four-sided figure now.
Please on your sheet of paper describe the type of four sided figured that you have made. Now is a great time to talk about rhombus, squares, rectangles, diamonds, acute, obtuse, degrees in a quadrilateral polygon, etc.
Please build a five sided figure. Please describe what this five sided figure looks like. What is a five sided figure called? Is this five sided figure regular or irregular?
Now is a great time to look at this picture above. If you notice there are a total of six balls which would mean six angles. Therefore this shape could look as though it is a six sided figure. These tools to create some issue with being able to discuss this because of their limitations. Although this could technically be viewed as a six sided figure, one of the angles is exactly 180°. 180° equals a straight line, therefore it does not count as an angle and that makes this a five sided figure. Building shapes becomes difficult with the variances of angles. Below you can see another picture where we continue this experiment. We ended with octagons.
In building each of these polygons we discuss the differences in the number of decreased found in each sided figure. There was much discussion of regular versus irregular.
In wrapping up we discussed whether the shapes were two-dimensional or three-dimensional. This question was solely to start the next activity. It was a get them thinking about 2-D versus 3-D prior to beginning the activity following day.