It determines what part of a graph you see on the GRAPH screen.
What you see on the WINDOW screen depends on your Graph Mode.
In all graph modes, xmin and xmax give the smallest and largest x-coordinates on the screen, and ymin and ymax give the smallest and largest y-coordinates on the screen.
(These variables, like the other variables that show up on the WINDOW screen, are system variables; you can't assign them different meanings. You can, however, give them values on the command line of the HOME screen with the STO command.)
xscl and yscl determine where tick marks appear on the axes (and where grid marks appear if Grid is ON in the Graph Formats menu.) Setting them equal to 0 removes the tick marks.
The Tools
menu works much as it always does. F1,9 gives you the same Graph
Formats menu you get from the GRAPH screen.
The Zoom
menu gives you the same options you have on the GRAPH screen. Choosing
one overrides the WINDOW entries and takes you straight to the GRAPH screen.
In FUNCTION mode, the other variable is xres, which determines how often (measured in pixels) the calculator recomputes the coordinates. Lower values make for more accurate graphs. Higher values make for quicker graphing, since the calculator has fewer dots to connect.
A ratio of
7 to 3 (as shown) for the length of the x-axis and the y-axis gives approximately
equal scales
on the TI-92+.
A ratio
of 25 to 12 for the length of the x-axis and the y-axis gives approximately
equal scales on the TI-89.
In PARAMETRIC
mode, tmin
and
tmax determine the smallest and largest values
of t which produce points to be plotted, and tstep determines the
change in t between successive points.
You almost
exactly the same thing in POLAR mode, with t replaced by theta.
In SEQUENCE
mode, nmin and nmax determine which terms of the sequence
are calculated.
plotStrt
and plotStep determine which terms of the sequence are plotted.
(This does
make sense. In some sequences, you need to know earlier terms to calculate
later ones. So you might need to calculate the first 10 terms to get the
rest of them, but you may want to start plotting with the 11th
term.)
The calculator
plots sequences by using the number of the term as the x-coordinate and
the value of the term as the y-coordinate.
In 3D mode,
the eye variables determine how the graph is oriented on the screen.
Since you can adjust that with the cursor keys anyway, you can ignore them.
xgrid
and ygrid specify the number of grid lines drawn. Larger numbers
give better pictures, but slow down the calculator.
ncontour
determines the number of contour lines (curves consisting of points all
with the same z-coordinate) the calculator will draw. You have a choice
in the Graph Formats menu whether you want any contour lines at all (they're
very slow to draw), but you need a number on the WINDOW screen even if
that option is OFF.
DIFF EQUATIONS mode lets the calculator plot graphical solutions to differential equations in several ways. Consult your owner's manual for details.