# Geometer Features

Complete documentation is available online, either here on the web at Geometer Documentation, or in Postscript or Acrobat format. The reference manuals are large (1.5 megabytes for the PostScript file and about 2 megabytes for the Acrobat version), so if you just want to get the flavor, take a look at the online version which is divided into dozens of smaller pages.

## Executive Description

Geometer is a constraint-based drawing program for constructing and manipulating drawings in plane euclidean geometry. You can draw points, lines, circles, angles, arcs, et cetera. What is interesting is that if you've drawn two points and then the line passing through them, if you move one of the points, the line will also move in such a way that it continues to pass through the two points.

The program should be very useful for students and teachers of plane euclidean geometry. The program comes with a number of interesting examples.

Geometer runs on Windows systems (I have tested it on XP, NT, 98, and ME), Macintosh with OS X and on Linux systems.

## Feature List

• Geometer supports points, lines, circles, angles, conic sections, arcs, and Bézier curves.

• Geometer continuously recalculates constraint-based drawings as vertices are moved.

• Geometer uses a point-and-click graphical user interface for most things, but there are some quite interesting features available to the advanced user.

• A "proof" mechanism is available for the presentation of step-by-step proofs. Geometer does not prove theorems; a teacher would prepare a proof file, and by clicking on a button, students are led, step-by-step, through the proof.

• Geometer can test diagrams for interesting features. For example, if you drew a triangle and all its medians and then asked Geometer to test the diagram, it would report that the three medians meet at a point. This example is not too interesting, perhaps, but it also finds things like congruent angles, four points lying on a circle, et cetera.

• Geometer has a script mechanism that can transform a drawing through a fixed series of configurations.

• Geometer diagrams can be saved in Encapsulated PostScript format suitable for use in publications.

• All files are in ASCII format so Geometer diagrams can be edited or created with text editors or computer programs. In fact, you can edit the ASCII version from within Geometer and thus use a combination of GUI and text-based modification of the diagram.

• Geometer is small -- the executable is only a bit more than 0.5 megabytes.