192 Chapter 11: Differential Equation Graphing
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 192 of 26
8. Return to the Y= Editor. Press:
ƒ 9
— or —
TI-89: ¥ Í
TI-92 Plus: ¥ F
Set Fields = DIRFLD.
9. Press:
TI-89: 2‰
TI-92 Plus: ‰
Confirm that the axes are set
as shown.
10.In the Y= Editor, clear the
initial conditions for yi1 and
yi2.
11.Return to the Graph screen,
which displays only the
direction field.
12.To graph a family of solutions,
return to the Y= Editor and
enter the initial conditions
shown below.
yi1={2,6,7} and yi2={5,12,18}
13.Return to the Graph screen,
which displays a curve for
each pair of initial conditions.
14.Press …to trace. Then press
3 ¸ to see the number of
foxes (xc) and rabbits (yc) at
t=3.
Because t0=0 and tmax=10,
you can trace in the range
0 t 10.
Note: In this example,
DIRFLD
is used for two
related differential equations
that do not represent a 2nd-
order equation.
Tip: Use a list to specify
more than one initial
condition.
Tip: Use
C
and
D
to move
the trace cursor from one
initial condition curve to
another.