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Entering and solving differential equations, Graphing in slpfld format – Texas Instruments TI-86 User Manual

Page 151

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Chapter 10: Differential Equation Graphing

139

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 139 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 139 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 139 of 20

Entering and Solving Differential Equations

In

Func

graphing mode,

x

is the independent variable and

y

is the equation variable. To avoid

conflict between

Func

equations and

DifEq

equations on the TI

-86,

t

is the independent

variable and

Q'

n

is the equation variable in

DifEq

graphing mode. Therefore, when you enter

an equation in the differential equation editor, you must express it in terms of

t

and

Q'

n

.

For example, to express the first-order differential equation y'=x

2

, you would substitute

t

2

for x

2

and

Q'1

for y', and then enter

Q'1=t

2

in the equation editor.

Graphing in SlpFld Format

ᕡ Display the mode screen and set

DifEq

graphing mode.

- m # # #
# " " " b

ᕢ Display the format screen and set

SlpFld

field format.

6 / & #
# # # # b

ᕣ Display the equation editor and store the

differential equation y'=x

2

, substituting

Q'1

for y' and

t

for x. Clear any other

equations.

& & I

ᕤ Display the initial conditions editor and

enter the initial conditions. A small square
indicates that an initial condition is required.

- g

3

In the example, the default
window variable values are
set initially.