Texas Instruments TI-86 - Manual (Page 147)

Chapter 10: Differential Equation Graphing
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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 20 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 20 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 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 àor 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  (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.