# Is there online geometric construction software that models physical constructions?

In this weird pandemic school year, I'm doubly interested in technology integration to help my virtual (high school) students as much as my in-person students. I've been particularly eager to get that working with compass-and-straightedge constructions. Obviously, students need a little familiarity with holding a compass and making accurate markings without injuring themselves, but learning and practicing the steps of the necessary constructions could be more convenient with virtual tools instead of real ones.

My problem is that I really don't like how Geogebra and other tools (like IXL and Euclidea) manage constructions. There are two main drawbacks that I can identify. The first is that they all use compasses to make circles instead of arcs. For instance, here is the traditional look of a successful angle bisection versus the same construction where full circles are drawn. Frankly, I find it barely recognizable.

The second flaw is that the "rusty compass" style of setting a compass size and then drawing a number of arcs with that radius is not native to the apps. Rather, the "compass" setting on all of these tools require you to set a radius (via two points or a line segment) for each circle drawn. Both of these drawbacks keep Geogebra, IXL, and Euclidea from effectively simulating what a real-world compass-and-straightedge construction looks and feels like.

Does anyone know of an online tool that would do a better job? I'm imagine an interface where the compass operations would be changing the radius and making a circle. The latter would have you pick the center, draw a faint complete circle, let you choose the arc(s) of the circle you wanted, and then erase the complete circle when you were done. I seem to recall that the Smart Board construction interface is somewhere along these lines, but I'm looking for a sandbox that students can play with on their chromebooks or smart phones.

• Not what you asked for, but there are 2 sites I love. They've gamified construction, but do use the geogebra model (1 uses geogebra, the other seems similar). euclidthegame.com and sciencevsmagic.net/geo Oct 27, 2020 at 4:24
• Mathematica has impressive capabilities related to what you are looking for. See reference.wolfram.com/language/ref/GeometricScene.html and many related features listed at reference.wolfram.com/language/guide/SyntheticGeometry.html Oct 27, 2020 at 21:13
• @SueVanHattum Another game in that vein that I managed to get some kids onto at one point is called "Euclidea.xyz" (web, iOS, android). The same developers have an app "Euclidea: Sketches" which attempts to be more of a geogebra-like sandbox on their engine. It's fairly nice. Oct 27, 2020 at 21:49

This looks promising but it is not free: mathspad.co.uk.

You can experiment with the tools without creating (or paying for) an account:

Have you checked out Math Open Reference? The site has animations that demonstrate how to do the constructions, in the style that you indicated. It won't let students DO the construction online; instead it shows them the steps necessary to do the construction. It also includes printable worksheets for them to practice doing it by hand as well as providing an explanation (proof) of why it works.

The link below is for the amination of the angle bisector construction.

https://www.mathopenref.com/constbisectangle.html

Are you aware you can choose not to show objects or labels with Geogebra? You can draw arcs, but at first the bounding points will be shown too, but you can hide them afterwards, as in this example:

I think https://www.robocompass.com/ fits the bill... if you are ok with something code-driven, which for me is just an amazing bonus for my students and for exposition.

So, the way in which robocompass deviates from rusty compass is directly related to a major potential benefit. Worth a look, anyway!

you can consider using https://cabricloud.com/cabriexpress/secondary/

There is an on screen compass, protractor, ruler and set square.