Texas Instruments TITANIUM TI-89 User Manual
Page 422

Differential Equation Graphing
422
If You Do Not Enter an Initial Condition in the Y= Editor
If You Do Not Enter an Initial Condition in the Y= Editor
If You Do Not Enter an Initial Condition in the Y= Editor
If You Do Not Enter an Initial Condition in the Y= Editor
If you do not enter initial conditions, the
ncurves
Window variable (
8 $) specifies
the number of solution curves graphed automatically. By default,
ncurves = 0
. You can
enter a value from 0 through 10. However, the
Fields
graph format and the
Axes
setting
determine whether
ncurves
is used.
When
ncurves
is used,
t0
is set temporarily at the middle of the Graph screen. However,
the value of
t0
as set in the Y= Editor or Window Editor is not changed.
Notes:
•
Without entering initial conditions, use SLPFLD (with
ncurves=0
) or DIRFLD to
display a slope or direction field only.
•
SLPFLD is for a single 1st-order equation only. DIRFLD is for a 2nd-order equation
(or system of two 1st-order equations) only.
If Fields =
Then:
SLPFLD
Uses ncurves, if not set to 0, to graph curves.
DIRFLD
Ignores ncurves. Does not graph any curves.
FLDOFF
Uses ncurves if Axes = TIME (or if Axes = Custom and the
x axis is t). Otherwise, a Diff Eq setup error occurs.