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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6 Responses to Dynamic Geometry

  1. Mr. H says:

    I’m no expert in either, but one HUGE advantage of GeoGebra is that it’s free. Kids can go to GeoGebra Download page and run the program at home by installing using web start or run them online by using applet start.

    You can also easily export the GeoGebra files to applets and post it online so kids can access them at home and play with them. I’ve only started learning GeoGebra this summer and so far I’m impressed with what’s possible. Here are some things that I’ve tried so far.

  2. Dan says:

    You know that’s an excellent point. Free beats Paid every time, especially when you want the kids to buy (haha) into the software. Thats a major plus in the geogebra column.

  3. David Cox says:

    To answer the last question first: GeoGebra. Hands down. I’m no expert with GSP, but I’ve found it very difficult while GGB is much more intuitive for myself as well as my students. As Sheng pointed out, free helps too. There is a very supportive community of GGB folks as well who are very willing to share resources and help with any questions you may have.

    I like the lab idea but would strongly recommend a lab or two where stident’s get a chance to poke around to learn the difference between a drawing and a construction as well as familiarize themselves with all of the tools. After that, your labs can be much more hands off for you and hands on for them.

  4. Susan Socha says:

    I agree that for kids, Geogebra is free–a big plus. The other thing I like is that what you create in Geogebra can go into a webpage and look exactly like what you created. Javasketchpad does NOT do this! The down side of Geogebra is that you have to rely on people to answer your pleas for help, and although they are very responsive on their forum, you don’t learn how to do it yourself! I don’t know LATEX so whenever I have to do something a little strange I have to get someone to tell me how to write the LATEX command. There is some amazing stuff out there in Geogebra on the web, but you have to really search for it. It is also not as user friendly in general as Sketchpad. Hope this helps.

  5. Dan says:

    Well you’ve all convinced me to give geogebra a solid effort. A disadvantage is that I’ve gotten a bunch of the (somewhat stodgy) department to learn sketchpad so I’ll be leaving them behind. Then again those who did learn sketchpad just use it to make pretty diagrams for quizzes/tests.

    p.s. How the heck do you pronounce geogebra?

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