The Geometer’s Sketchpad
®
for TI-89, TI-92 Plus, and
© 2000-2002 KCP Technologies, Inc.
34
Voyage™ 200 PLT User Guide and Reference Manual
Custom tools are tools you define yourself for adding new constructions to
the toolbox. Just as the basic toolbox comes with tools for constructing
segments, rays, lines, and circles given two points, you can make new
construction tools that construct any object—or any set of objects—given
one or more points (or other objects). For example, you can create tools to
construct triangles, special triangles (such as equilateral triangles), or more
complex sets of objects. You can also create tools that construct single
basic objects (such as lines and circles) in new ways. For instance, you can
make a tool that, given a segment, creates the perpendicular bisector of that
segment, or a tool that, given three points, constructs the circle passing
through those three points. Custom tools allow you to re-use constructions
easily and efficiently.
Before creating custom tools, it’s useful to review some facts about
geometric constructions. All objects in a construction may be divided into
three groups. The independent objects, or givens, are objects that are
necessary for the construction but that are not defined by the construction.
The dependent objects are objects that are defined by the givens—or by
other dependent objects in the construction. These dependent objects may
be divided into results, which are the objects of ultimate interest in the
construction, and intermediate construction objects, which are dependent
objects necessary to produce the results but not of particular interest
themselves. Here are some examples:
Construction
Objects
General Triangle
Givens: 3 points
Construction Objects: none
Results: 3 segments
Perpendicular Bisector between Points
Givens: 2 points
Construction Objects: 1 segment,
1 midpoint
Results: 1 perpendicular line
Custom Tool
This section introduces custom tools—Sketchpad’s advanced
facility for creating new tools and adding them to the toolbox.
Custom tools allow you to enrich Sketchpad’s mathematical
vocabulary with as many new operations as you wish. You
should be familiar with Sketchpad’s basic operations before
attempting to make custom tools.
About Custom
Tools
If you’re familiar with The
Geometer’s Sketchpad for
desktop computers, custom
tools are similar to desktop
Sketchpad’s “script tools.”
