Construct Regular Polygons Inscribed in Circles

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SWBAT construct equilateral triangles, squares, and regular hexagons in circles

Big Idea

Construction without Blueprints? Is that permitted?

Sketchpad Construction Demonstrations

10 minutes

In this lesson, students will be performing classic constructions using only compass and straightedge. My goal in this section is to use Sketchpad to show them the constructions they'll be doing and to introduce some important concepts that will come in handy when they have to problem-solve and figure out how to perform the constructions.

Check out this screencast to learn more about the demonstration I do for my students.

Student Constructions

20 minutes

In the previous section, I've given students all of the hints they're going to get for now. In this section they'll be working on Student Constructions. I pass out the resource and the construction challenge is on. I do my best to create an atmosphere of challenge, puzzlement, problem-solving, etc. 

As students are thinking and working, I'll walk around and see how things are going. I evade the "Is this right?" question, but I will stand and listen to students' reasoning then most often offer a cryptic "Hmmm..."

This is also a time for me to identify some student exemplars for later when I have students come to the document camera to demonstrate and explain their work.


Student Presentations

20 minutes

In this section, I will call students who I have identified as exemplars to present each of the constructions, explain the steps they took and the geometry that makes them achieve the desired results. I will also ask if there are any students who performed the constructions in a different way and still got good results. It's possible that I have failed to identify a good exemplar and I don't want to miss out on discussing an innovative, non-typical, approach.

Transfer Task

10 minutes

To see if students can apply what they've learned in this lesson to a slightly novel situation, I'll have them construct a regular octagon inscribed in a circle. Students will get 15 minutes alone with the Transfer Task to see what they can produce and explain.