Texas TI-86 User Manual
Chapter 10: Differential Equation Graphing
137
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 137 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 137 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 137 of 20
Setting the Axes
To display the axes editor, select
AXES
from the
GRAPH
menu in
DifEq
mode (6 )).
x=
assigns a variable to the x-axis
y=
assigns a variable to the y-axis
dTime=
specifies a point in time (real number)
fldRes=
(resolution) sets number of rows (1 through 25)
At the
x=
and
y=
prompts, you can enter the independent variable
t
, as well as
Q
,
Q'
,
Q
n
, or
Q'
n
, where n is an integer
‚ 1 and 9. If you assign
t
to one axis and
Q
n
or
Q'
n
to the other
axis, only the equation stored to
Q
n
or
Q'
n
is plotted; other differential equations in the
equation editor are not plotted; their selection status is ignored.
dTime
is only valid for
second-order equations with
t
in either equation.
The axes editor and defaults for each field format are shown below. When
SlpFld
field
format is set, the x-axis is always
t
, so the
AXES: SlpFld
editor does not display
x=t
.
When
SlpFld
format is set:
When
DirFld
format is set:
When
FldOff
format is set:
Differential Equation Graphing Tips
♦
Since the TI
-86 plots slope fields and direction fields before it plots equations, you can
press b to pause the graph and view the fields with no solutions plotted.
♦
If you do not specify initial conditions for the equations assigned to the axes, the TI
-86
simply draws the field and stops. This gives you access to both the field format options
and the interactive initial conditions simultaneously.
and the interactive initial conditions simultaneously.
Axes information is stored to
GDB
and
PIC
variables.