There are two basic types of geometry software -- dynamic and non-dynamic. Dynamic software needs either a Macintosh or IBM with Windows 3.1 or later. This software allows you to drag parts of constructions around while the measurements change on the screen. This software allows you to trace a point, line, etc. while something moves. You can also animate parts of a construction.
Geometer's Sketchpad - Key Curriculum Press - $170 1-800-995-MATH 2512 Martin Luther King Jr. Way P.O. Box 2304 Berkeley, CA 94702-0304 http://www.keypress.com Also allows you to put axes and grid on the screen to graph. Integrates algebra and geometry. My personal favorite.
Geometry Inventor - LOGAL, Inc. - $200 1-800-LOGALUS also carried by Sunburst 1-800-321-7511 101 Castleton Street P.O. Box 100 Pleasantville, NY 10570-0100 This software has a menu of pre-programmed shapes. For example, you can select an isosceles triangle, measure selected parts, then drag to see a wide variety of isosceles triangles. I did not find animation as easy as with the Sketchpad.
Cabri Geometry - Texas Instruments - ? (about $160) You need to go through a distributor. I use SchoolMart. 1-800-285-2662 P.O. Box 80 Gambrills, MD 21054 TI also has a web site. This software is also on the TI-92 graphics calculator. You can put axes on the screen with this software also.
With both Cabri and Sketchpad, you must construct your figures. For example, it you want an isosceles triangle, you have to know what the definition says and construct it accordingly. All of the above do all the transformations -- reflections, translations, rotations, and dilations.
Non-dynamic software: GeoExplorer - Scott Foresman - $120 for a site license. This software was designed to go with the University of Chicago School Math Project, but can be used with any textbook. It has menus for the different objects to be constructed. You can put a grid on the screen and plot points. It does all the transformations. You would have to check with your local school for the Scott Foresman representative for your area.
Geometric Supposers: Quadrilaterals and Triangles - $99 each Sunburst 1-800-321-7511 101 Castleton St. P.O. Box 100 Pleasantville, NY 10570-0100 This software is menu driven -- one for quadrilaterals and one for triangles. You cannot do triangles with the quadrilateral software, and vice versa.
For non-dynamic software, to investigate theorems or attributes of a particular figure, you need to draw several and then look for similarities. With dynamic software, you construct one and then drag it to form a wide variety of others. The non-dynamic programs do not need Windows, but run on DOS. They are the older technology, but are cheaper. GeoExplorer is really quite powerful and includes all the polygons and circles in one software.
The TI-92 graphics calculator is about $160 from many distributors, including the local discount stores. I found that the advertised price at local stores is about $10 more than mail order, but you avoid shipping changes. It may be a wash. This calculator has Cabri Geometry and Derive (algebra manipulator for algebra, calculus, etc.) It also has the usual calculator features, graphing, statistics, etc. Can connect to computer (Graph Link costs about $45) and CBL (Calculator Based Laboratory). The CBL uses probes to do science experiments and collect and analyze data.
Good luck and good hunting. Check out what your local school is using.
Eileen Schoaff Buffalo State College Buffalo, NY 14222