Texas Instruments PLUS TI-89 - Manual (Page 216)

Chapter 11: Differential Equation Graphing 199
11DIFFEQ.DOC TI-89/TI-92 Plus: Differential Equation (English) Susan Gullord Revised: 02/23/01 11:04 AM Printed: 02/23/01 2:15 PM Page 199 of 26
In the
Y= Editor If you enter a 2nd- or higher-order equation, enter it
as a valid system of equations as described on
page 186.
All equations (selected or
not) must have the same
number of initial
conditions. Otherwise, a
Dimension error occurs
when you graph.
To set Axes = TIME or CUSTOM, press:
TI - 89 : 2 ‰
TI - 92 Plus: ‰
With custom
axes If X Axis is not t , you must enter at least one initial
condition for each equation in the Y= Editor
(whether the equation is selected or not).
Otherwise, a Diff Eq setup
error occurs when you
graph.
In the Graph
screen If no curve is graphed, set an initial condition as
described on page 184. If you did enter initial
conditions in the Y= Editor, select
ZoomFit:
TI - 89: „ j A
TI - 92 Plus: „ A
A 1st-order equation may look different with FLDOFF
than with SLPFLD . This is because FLDOFF uses the
tplot and tmax Window variables (page 181), which
are ignored with SLPFLD .
Notes For 1st-order equations, use FLDOFF and
Axes = Custom to plot axes that are not possible with
SLPFLD . For example, you can plot t vs. y1' (where
SLPFLD plots t vs. y1 ). If you enter multiple 1st-order
equations, you can plot one equation or its solution
vs. another by specifying them as the axes.
You can use the Table screen to view the points for a differential
equation graph. However, the table may show different equations
than those graphed. The table shows only the selected equations,
regardless of whether those equations will be plotted with your
current
Fields and Axes settings.
Fields=FLDOFF
If You Use the Table
Screen to View
Differential
Equations