Texas Instruments PLUS TI-89 - Manual (Page 199)

182 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 182 of 26
xmin , xmax ,
ymin , ymax
Boundaries of the viewing window.
xscl , yscl Distance between tick marks on the x and y axes.
ncurves Number of solution curves (0 through 10) that will be
drawn automatically if you do not specify an initial
condition. By default,
ncurves = 0 .
When ncurves is used, t0 is set temporarily at the middle
of the screen and initial conditions are distributed
evenly along the y axis, where:
increment =
ymax ì ymin
ncurves + 1
The y values for the initial conditions are:
ymin + increment
ymin + 2
ù (increment)
©
ymin + ncurves ù (increment)
diftol ( Solution Method = RK only) Tolerance used by the RK
method to help select a step size for solving the
equation; must be
‚1 E ë 14.
fldres ( Fields = SLPFLD or DIRFLD only) Number of columns
(1 through 80) used to draw a slope or direction field
across the full width of the screen.
Estep ( Solution Method = EULER only) Euler iterations
between tstep values; must be an integer >0. For more
accuracy, you can increase Estep without plotting
additional points.
dtime ( Fields = DIRFLD only) Point in time at which a
direction field is drawn.
Standard values (set when you select 6:ZoomStd from the „ Zoom
toolbar menu) are:
t0 = 0. xmin = ë 1. ymin = ë 10. ncurves = 0.
tmax = 10. xmax = 10. ymax = 10. diftol = .001
tstep = .1 xscl = 1. yscl = 1. Estep = 1.
tplot = 0. fldres = 14.
dtime = 0.
You may need to change the standard values for the t variables to
ensure that sufficient points are plotted.
Window Variables
(Continued)
Note: For information about
how the Fields graph format
affects whether ncurves is
used, refer to page 184.