The Geometer’s Sketchpad
®
for TI-89, TI-92 Plus, and
© 2000-2002 KCP Technologies, Inc.
76
Voyage™ 200 PLT User Guide and Reference Manual
Choose Mark Coordinate System or Mark Axes to make a non-active
coordinate system active. Sketchpad plots points or functions on the active
coordinate system. Similarly, Sketchpad measures coordinates and
equations in reference to the active coordinate system. In a sketch with
multiple coordinate systems, use Mark Coordinate System or Mark Axes
to switch between active coordinate systems, as described in the following
steps.
1.
Show the grid of the non-active coordinate system if it is not already
showing. (See Show All Hidden, page 53).
2.
Select the non-active coordinate system by positioning the Arrow tool
at one of its grid points and pressing
¸
.
3.
Press
ˆ
Graph:
©
Mark Coordinate System
(TI-89:
2 ˆ
Graph:
©
Mark Axes). Sketchpad activates the
selected coordinate system and confirms the activation with a brief
animation. Future plotting and measuring will be conducted in
reference to the activated coordinate system.
If a sketch has only one coordinate system, there is no need to use Mark
Coordinate System or Mark Axes.
Use the Graph Form menu to create a new Square, Rectangular, or
Polar coordinate system in a sketch with no coordinate system or to switch
the active coordinate system between square, rectangular, and polar shapes.
Note that if you have defined the active coordinate system in terms of a
single unit length (for instance, by Define Unit Distance or Define Unit
Circle), you can switch it between square and polar shapes, but you cannot
switch it to a rectangular shape (because rectangular coordinate systems
must be defined by two unit lengths). Similarly, if you have defined a
coordinate system in terms of two unit lengths (Define Rectangular
Coordinates), you cannot make it square—except by making the two unit
lengths equal. Sketchpad makes available only the Graph Form
commands that are appropriate to the active coordinate system.
Choose Show Grid to show the grid associated with the active coordinate
system. Choose Hide Grid to hide a visible grid.
(You may also show and hide grids as you would other objects—using
Show All Hidden from the Display menu or by selecting them and
choosing Hide Object from the Display menu. However, it’s usually more
convenient to show and hide the grid directly with a single command.)
Choose Snap To Grid to force dragged points to snap to grid points. When
Snap To Grid is active, a checkmark appears next to it in the Graph
menu. Choose Snap To Grid a second time to return to normal dragging.
Snap To Grid is useful when investigating coordinatized constructions in
which you’d like dragged points to always have whole number
coordinates.
Mark Coordinate
System (TI-92 Plus
/Voyage™ 200 PLT)/
Mark Axes (TI-89)
Graph Form
Show/Hide Grid
See Performance Tips
(page 86) for important tips
about working with grids.
Snap To Grid