Texas Instruments TI-89, TI-92

Chapter 11: Differential Equation Graphing 181

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 181 of 26

In the Y= Editor, Axes may or may not be available, depending on the

current graph format.

If it is available, you can select the

axes that are used to graph the

differential equations. For more

information, refer to page 190.

TI-89: 2‰

TI-92 Plus: ‰

Axes Description

TIME Plots t on the x axis and y (the solutions to the selected

differential equations) on the y axis.

CUSTOM Lets you select the x and y axes.

Differential equation graphs use the following Window variables.

Depending on the Solution Method and Fields graph formats, not all of

these variables are listed in the Window Editor ( ¥$) at the

same time.

Variable Description

t0 Time at which the initial conditions entered in the

Y= Editor occur. You can set t0 in the Window Editor

and Y= Editor. (If you set t0 in the Y= Editor, tplot is set

to the same value automatically.)

tmax,

tstep

Used to determine the t values where the equations are

plotted:

y'(t0)

y'(t0+tstep)

y'(t0+2ùtstep)

... not to exceed ...

y'(tmax)

If Fields = SLPFLD, tmax is ignored. Equations are

plotted from t0 to both edges of the screen in tstep

increments.

tplot First t value plotted. If this is not a tstep increment,

plotting begins at the next tstep increment. In some

situations, the first points evaluated and plotted

starting at t0 may not be interesting visually. By setting

tplot greater than t0, you can start the plot at the

interesting area, which speeds up the graphing time

and avoids unnecessary clutter on the Graph screen.

Setting Axes

Window Variables

Note: If

tmax < t0

tstep

mus

be negative.

Note: If

Fields=SLPFLD

tplot

is ignored and is

assumed to be the same