Texas Instruments TI-89 Voyage 200, User Manual

Page: 429 / 1008

Differential Equation Graphing 429
If you select
ZoomSqr
(
„
5
), you can see that the phase-plane orbit is actually a circle.
However,
ZoomSqr
will change your Window variables.
6. In the Y= Editor, press:
@ 2
‰
and make sure
Axes = CUSTOM
with
y1
and
y2
as the
axes.
Important: Fields=DIRFLD
cannot plot a
time axis. An
Invalid Axes
error occurs if
Axes=TIME
or if t is set as a
CUSTOM
axis.
7. In the Window Editor (
8 $
), set
the Window variables.
t0=0
tmax=10
tstep=.1
tplot=0
xmin= L 2
xmax=2
xscl=1
ymin=
L
2
ymax=2
yscl=1
ncurves=0
diftol=.001
fldres=14
dtime=0
8. Display the Graph screen (
8 %
).
x axis = y1 = y
y axis = y2 = y'