Monday, December 9, 2013

Learning GeoGebra - Part 2

Working on my project for Math 641 has forced me to learn a lot more about GeoGebra.  Some of the manipulatives for the propositions in Book III were quite simple, but others had a lot going on.  Here are some of the new things that I learned:

How to define a figure made up of two or more other objects
I first ran into this issue when I was trying to make a picture for a circular segment.  I couldn't find a tool (and maybe there is one?) to make a segment that I could fill and color.  After a few Google searches, I found instructions for how to create a list.  In the input line at the bottom of the GeoGebra window I used set braces to enter the following, for example

     {Segment[A,B], Arc[c,B,A]}

This would define the figure bounded by line segment AB and the arc on circle c between B and A.  It showed up as a list in the algebra pane, which I could select and give a color to for emphasis.  Of course, different types of figures could be included in a list, but I used these mainly to create segments, since my work was with circles.

More varied ways of assigning conditions to show objects
In an earlier post, I explained how I had learned to use check-boxes and sliders to show and hide figures.  For many the manipulatives that I was making for the propositions, I wanted things to change color or have tick marks added to them when lengths or angles were the same.  I learned how to put measures other than a slider value in the conditions to show object line in object properties.  I used the distance between points,


frequently.  I also learned how to include measures of objects that were in a worksheet by using their letter names, which required using the "alpha" button on the right side of the dialogue box for angles.  If I wanted measures to be within a certain range of one another, I used the absolute value of their difference, for example


As I mentioned, I often used these to make segments change color when they were congruent, or to have tick marks added.  Most of the time, I had constructed completely separate segments with the different colors or marks.  It wasn't until I was almost done with the project that I realized if color was the only thing I wanted to change, I could put conditions in the "Dynamic Colors" settings right below "Condition to Show Object" (so obvious!).  However, it was still nice to be able to change line styles and thicknesses in addition to color.

I understand that these are very simple things for more seasoned GeoGebra users, and they do seem simple to me now.  They were new ground for me as I worked on my project, though, and each one was a hurdle that I had to work through to make each of my manipulatives work the way they were supposed to.

If you know of easier ways to do the things described above, I'd love to know!  Please leave a comment.

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