Dynamic Geometry

Dynamic Geometry Software

I have access to Geometer’s Sketchpad at school; its installed on a bunch of laptops and in a couple of computer labs.  Geogebra is a similar program but I do not have much experience with it.

For the past 4 years I’ve done various “labs” with the Geometry students where they create a set of objects in sketchpad and then measure the different characteristics.  From these measurements they are supposed to write a corresponding theorem to fit the data.  For instance they would create the following object: They would then measure the angle CAO and the arc ADB to find out that the measure of the angle is exactly half that of the arc.  The top quarter of students would have this written down after putting some words in their pencil: “The measure of the angle formed by a tangent and a chord is half the measure of the arc that is inside“.  My “putting words in their pencil” is the following leading question:

(the full document and its 49 steps are here: http://drop.io/circleAnglesLab )

49 steps? Are you kidding?

Am I giving the students too much help?

(or as Dan Meyer would say: “be less helpful”)

The reason there are 49 steps to the document is that this is the first time the students are seeing geometer’s sketchpad and it’s less than intuitive on how to measure an angle or an arc with this software.  The document was created when I thought that it’d be best to give the kids as precise of a path as possible to the truth.

Overall I think this type of project is a good idea for how to teach some sections of geometry, but I’d like to be less focused on the steps and more focused on the material.  Many students would carefully go through the steps and get to the end with the theorems written correctly, but still mess up the proper theorems on the assessments.

Where should I go from here?

Maybe I should have an intro “lesson” on how to use sketchpad to measure circles (demo how to measure an arc) and then set them free with a goal (Find the measure of an inscribed angle in relationship to an arc).  High expectations are an excellent thing in a classroom, but am I asking the all the Oilers to be The Great One?

Last Question.

For those Sketchpad and Geogebra experts out there, would you recommend Geogebra over Sketchpad?  I haven’t had enough time yet this summer to start playing with Geogebra and so I only have a very basic understanding of it.  Thanks!

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