Texas Instruments TITANIUM TI-89 User Manual

Page 419

Differential Equation Graphing

419

Standard values (set when you select

6:ZoomStd

from the

„

Zoom

toolbar menu) are:

You may need to change the standard values for the t variables to ensure that sufficient
points are plotted.

The fldpic System Variable

When a slope or direction field is drawn, a picture of the field is stored automatically to a
system variable named

fldpic

. If you perform an operation that regraphs the plotted

equations but does not affect the field, the TI-89 Titanium reuses the picture in

fldpic

instead of having to redraw the field. This can speed up the regraphing time significantly.

fldpic

is deleted automatically when you exit the differential equation graphing mode or

when you display a graph with

Fields = FLDOFF

Exploring a Graph

As in function graphing, you can explore a graph by using the following tools. Any
displayed coordinates are shown in rectangular or polar form as set in the graph format.

t0 = 0.
tmax = 10.
tstep = .1
tplot = 0.

xmin =

xmax = 10.
xscl = 1.

ymin =

10.

ymax = 10.
yscl = 1.

ncurves = 0.
diftol = .001
Estep = 1.
fldres = 14.
dtime = 0.

Tool

For Differential Equation Graphs:

Free-Moving
Cursor

Works just as it does for function graphs.