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Setting the initial conditions – Texas Instruments TI-86 User Manual

Page 148

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136

Chapter 10: Differential Equation Graphing

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 136 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 136 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 136 of 20

The values shown in the picture on page 135 are defaults in

Radian

mode.

x

and

y

settings

correspond to the axes variables (page 137).

$

indicates that

xScl=1

,

yMin=

L

10

,

yMax=10

,

yScl=1

,

and

difTol=.001

(in

RK

format) or

EStep=1

(in

Euler

format) are beyond the screen.

tMin=0

Specifies the

t

value at which to begin evaluating within a graph screen

tMax=6.28318530718

Specifies the last

t

value to evaluate within a graph screen

tStep=.1308969389958

Specifies the increment from one

t

value to the next

t

value

tPlot=0

Specifies the point at which plotting begins (ignored when

t

is an axis)

difTol=.001

(in

RK

format) Specifies tolerance to help select step size for solving; must be

‚ 1

E

L12

EStep=1

(in

Euler

format) Specifies Euler iterations between

tStep

values; must be an integer >0 and

 25

Setting the Initial Conditions

To display the initial conditions editor, select

INITC

from

the

GRAPH

menu (6 (). On this editor, you can set

the initial value at

t=tMin

for each first-order equation in

the equation editor.

tMin

is the first

t

value to evaluate.

Q

[

1

is the initial value of

Q

n

. A small square next to an initial condition variable

indicates that a value is required for a defined differential equation.

You can enter an expression, list, or list name for initial conditions

tMin

and

Q

[

n

. When you

enter a list name, the elements are displayed when you press b, # or $.

If

SlpFld

or

DirFld

format is set, you need not specify initial conditions. The TI

-86

returns the appropriate field with no specific solutions.

If

FldOff

format is set, you must specify initial conditions.

tMax

default is 2

p

.

tStep

default is

24.

Initial conditions information
is stored to GDB and PIC
variables.