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Cabri Jr. versus GeoMaster on the TI-84 Plus Calculator

By C. C. Edwards

Because the TI-84 Plus comes equipped with two geometry applications, Cabri Jr. and GeoMaster, you can now do your geometric investigations on the calculator. Granted, the calculator screen is rather small for some investigations, but other than that, these two calculator applications do almost everything that the computer software packages do.

If you’ve ever used a dynamic geometry computer software package such as the Geometer’s Sketchpad or Cabri Geometry II Plus, then you appreciate its ability to not only accurately construct geometric figures, but to also perform translations, rotations, dilations, and reflections. These software packages can even take measurements, create tessellations, and much, much more. If you haven’t used such software packages, wouldn’t you like to?

To help you decide which application is best for you, consider the following differences between Cabri Jr. (version 1.03) and GeoMaster (version 1.10).

Some Cabri Jr. features not found in GeoMaster are

  • Cabri Jr. has an Undo tool; GeoMaster does not. However, they both allow you to delete a selected construction.

  • Cabri Jr. allows you to display constructions as dotted or solid lines; GeoMaster uses only solid lines.

  • Cabri Jr. has an Animate tool and a Locus tool; GeoMaster does not. Such tools allow you to show, for example, how the definition of a conic section is used to construct the conic section.

  • The Cabri Jr.’s Calculate tool can add, subtract, multiply, divide, and find square roots. GeoMaster’s Calculate tool can only add and subtract.

  • When you quit Cabri Jr. without saving your work, the next time you start the application your work appears as you left it. When you quit GeoMaster, your unsaved work vanishes.

  • Cabri Jr. can talk to (share files with) the Cabri Geometry II Plus computer software and to the Cabri Jr. applications found on the TI-89, TI-92 Plus, and Voyage 200 calculators. GeoMaster is not on speaking terms with anything.

Some GeoMaster features not found in Cabri Jr. are

  • GeoMaster has a tool for constructing any type of polygon, while Cabri Jr. has tools for constructing only triangles and quadrilaterals. In both applications, one can, of course, construct a polygon by stringing together consecutive line segments.

  • GeoMaster has a tool for constructing regular polygons; Cabri Jr. does not.

  • GeoMaster allows you to construct points by entering their coordinates; Cabri Jr. does not.

  • GeoMaster has three tools not found in Cabri Jr. that answer the questions: Are two lines parallel? Are two lines perpendicular? Are three points collinear?

  • As you move the cursor in GeoMaster, the coordinates of its location are displayed at the bottom of the screen. This feature is not available in Cabri Jr., although Cabri Jr. tells you the coordinates of a point after it is constructed. GeoMaster also allows you to adjust the size of the viewing window the same way you do when graphing functions.

  • GeoMaster can construct and add vectors; Cabri Jr. cannot.

  • GeoMaster can construct arcs of a circle; Cabri Jr. cannot.

  • GeoMaster has a tool that stores measured data (lengths, areas, and angle measures) in a list; Cabri Jr. does not. When the data is in a list, it can be accessed from the home screen, where you can perform more calculations on these measures than you can with Cabri Jr.