The Geometer’s Sketchpad
®
for TI-89, TI-92 Plus, and
© 2000-2002 KCP Technologies, Inc.
86
Voyage™ 200 PLT User Guide and Reference Manual
Take advantage of Sketchpad’s default selections. Whenever you construct
something, Sketchpad leaves the result selected. In many construction
sequences, you’ll use that result in your next step. You can frequently
reduce the amount of time you spend moving the cursor about if you
anticipate and take advantage of Sketchpad’s selections. In addition, many
of Sketchpad’s commands can operate on multiple selections
simultaneously. For instance, you can construct three parallel lines instead
of one by selecting a point and three lines, or a line and three points, before
constructing parallels.
The example below—the sixth midpoint heptagon of a heptagon—is made
up only of segments, but would take even an expert several minutes to
construct with the Segment tool.
The most efficient way to construct it
in Sketchpad is to create seven
selected points with the point tool.
(Hold down
2
when placing points
to keep them selected. On the TI-89,
make sure when placing multiple
selected points to use the
¸
key
instead of the
M
key shortcut in
order for the
2
key to have the
desired effect.) Then repeatedly
alternate between the Segments
command and the Midpoints
command from the
…
Construct
menu, without changing your
selections between commands. The
final figure can be constructed in just
a few seconds.
Loci and function plots are the most complex objects that Sketchpad
evaluates. In order to plot a locus or a function, Sketchpad must perform
thousands of internal calculations for each appearance of the plot.
Depending on their complexity, these objects may cause dragging to slow
down considerably.
Fortunately, you can control the complexity of Sketchpad’s internal
calculations. Each (locus or function) plot is composed of a number of
samples—positions at which the construction or function is being
Performance Tips
Sketchpad is a rich modeling environment for exploring
geometry and many forms of visual mathematics. But
mathematics is richer still. Mathematicians routinely ask
questions that even supercomputers can’t answer in any
reasonable amount of time! This section lists a few pointers
about optimizing the performance of The Geometer’s
Sketchpad for TI-89, TI-92 Plus, and Voyage™ 200 PLT.
Selection
Loci and Function
Plots
