Setting The Initial Conditions - Texas Instruments TI-89 Manual Book

Setting the Initial Conditions

Entering Initial
Conditions in the
Y= Editor
Note: For information about
defining a system for higher-
order equations, refer to
page 186.
If You Do Not Enter
an Initial Condition
in the Y= Editor
Tip: Without entering initial
conditions, use
SLPFLD
(with ncurves=0) or
DIRFLD
to display a slope or
direction field only.
Note: is for a single
SLPFLD
1st-order equation only.
is for a 2nd-order
DIRFLD
equation (or system of two
1st-order equations) only.
184 Chapter 11: Differential Equation Graphing
You can enter initial conditions in the Y= Editor, let the
calculate initial conditions automatically, or
TI-89 / TI-92 Plus
select them interactively from the Graph screen.
You can specify one or more initial conditions in the Y= Editor. To
specify more than one, enter them as a list enclosed in braces { } and
separated by commas.
To enter initial conditions for
the equation, use the
y1'
etc.
To specify when the initial
conditions occur, use t0.
This is also the first t
evaluated for the graph.
To graph a family of solutions,
enter a list of initial conditions.
For a 2nd- or higher-order differential equation, you must define a
system of 1st-order equations in the Y= Editor.
If you enter initial conditions,
you must enter the same number
of initial conditions for each
equation in the system.
Otherwise, a
Dimension error
occurs.
If you do not enter initial conditions, the
( ¥ $ ) specifies the number of solution curves graphed
automatically. By default,
0 through 10. However, the
determine whether ncurves
If Fields = Then:
Uses
SLPFLD ncurves
DIRFLD Ignores
Uses
FLDOFF ncurves
the x axis is
When is used,
ncurves
screen. However, the value of
Editor is not changed.
line,
yi1
ncurves
. You can enter a value from
ncurves = 0
graph format and the
Fields
is used.
, if not set to 0, to graph curves.
ncurves . Does not graph any curves.
if (or if
Axes = TIME
t ). Otherwise, a Diff Eq setup
is set temporarily at the middle of the Graph
t0
t0 as set in the Y= Editor or Window
Enter {10,20} even
though {10 20} is
displayed.
Window variable
setting
Axes
and
Axes = Custom
error occurs.