In the first of what I hope to be a (nearly) weekly column, I’ll review GeoGebra, a free geometry software package.

GeoGebra is similar to Geometer’s Sketchpad in that you can perform all of the standard ruler-and-compass constructions (e.g., bisecting a segment, bisecting an angle), but you can also enter algebraic equations. So if you want to work with a circle, you can enter the equation directly, or you can create a point and use it as the center to draw a circle with the “circle” tool (GeoGebra will then find the equation for you, if you want). Here’s the construction of a regular pentagon in progress (click for full-size):

The interface is fairly intuitive. I didn’t need to refer to the documentation at all to do my first construction (the pentagon). In my attempt to construct the heptadecagon, round-off error caused the last side to be off slightly, and I haven’t tried again lately (because really, who wants to follow the instructions to construct a 17-sided polygon *twice*?), so I don’t know if that has been fixed.

GeoGebra is Java-based, so it’s a little slow to load (as are all Java apps), but you can download the whole thing and install it locally. It’s a nice thing to have when you’re not at school and can’t get to Geometer’s Sketchpad, and it generates very nice pictures if you need to include some in a document (LaTeX, Word, a blog).

As a big fan of free software (which will become more apparent the more I review), I like GeoGebra. If you ever need a little help with those geometry constructions, you can’t find a cheaper solution.

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Tags: free software, GeoGebra, geometry

This entry was posted on November 9, 2007 at 7:25 am and is filed under Software, Teaching. You can follow any responses to this entry through the RSS 2.0 feed.
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November 9, 2007 at 8:15 pm |

Are there things that are typically done in Geometer’s Sketchpad that can’t be done in GeoGebra?

November 9, 2007 at 8:29 pm |

I’ve used Geometer’s Sketchpad all of…once, so I don’t really know what it’s capable of. According to this, GS can do animations, while GeoGebra can’t, but that appears to be it. There are few other features that GG has that GS doesn’t (such as exporting to PSTricks!), but I’d say they have essentially the same functionality.

November 29, 2007 at 6:42 pm |

Chris taught me how to use this, and I used it to make a picture for a paper I was working on. It was pretty easy, and the picture turned out great! Thanks Batman!

December 11, 2007 at 7:25 am |

There’s a 7-minute YouTube Geogebra tutorial by David Young here. It only shows the basics, but it’s easy to follow.

January 13, 2009 at 3:42 pm |

really it is very good and wonderfull, thanks for every one work in it ,

they help us a lot .

thanks

maha from Egypt

February 10, 2010 at 7:31 pm |

Hi. You may want to check out a GeoGebra Tutorial Series that I created here:

http://math4allages.wordpress.com/view-posts-by-topics/

Thanks.

September 16, 2010 at 4:12 pm |

There are also applets available at:

http://www.slu.edu/classes/maymk/GeoGebra/index.html