Calculator User Manual

Chapter 10: Differential Equation Graphing
135
10DIFFEQ.DOC TI-86, Chap 10, US English Bob Fedorisko Revised: 02/13/01 2:28 PM Printed: 02/13/01 3:02 PM Page 135 of 2010DIFFEQ.DOC TI-86, Chap 10, US English Bob Fedorisko Revised: 02/13/01 2:28 PM Printed: 02/13/01 3:02 PM Page 135 of 2010DIFFEQ.DOC TI-86, Chap 10, US English Bob Fedorisko Revised: 02/13/01 2:28 PM Printed: 02/13/01 3:02 PM Page 135 of 20
In this editor, you can enter and display a system of up to
nine first-order differential equations,
Q'1
through
Q'9
, if
sufficient memory is available. Equations are defined in
terms of the independent variable
t
and
à
or
Q'
.
You can refer to another differential equation variable in a
DifEq
equation, as in
Q'2=Q1
. However, you cannot enter a
list in a
DifEq
equation.
When the TI
-
86 calculates a differential equation system, it references all equations in the
equation editor, regardless of selection status, starting at
Q'1
. You must define
Q'
n
equation
variables consecutively, starting at
Q'1
. For example, if
Q'1
and
Q'2
are not defined, but you
attempt to solve an equation defined in
Q'3
, the calculator returns an error.
The TI
-
86 allows you to analyze each equation independently. For example, you can enter
Q'1=t
and
Q'2=t
2
and analyze each equation independently.
The TI
-
86 graphs only those selected equations that are appropriate for the specified axes.
♦
The default graph style is
¼
(thick) in
DifEq
mode.
♦
¾
(shade above),
¿
(shade below), and
Â
(dot) are not available in
DifEq
graphing mode.
Setting the Graph Screen Window Variables
To display the differential equation window editor, select
WIND
from the
GRAPH
menu (
6 '
).
DifEq
has the
same window variables as
Func
graphing mode, except:
♦
xRes
is not available in
DifEq
mode.
♦
tMin
,
tMax
,
tStep
, and
tPlot
are available in
DifEq
mode.
♦
difTol
(
RK
) and
EStep
(
Euler
) are available in
DifEq
mode.