194 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 194 of 26
9. Return to the Home screen,
and use BldData to create a
data variable containing the
Euler graphing points.
BldData eulerlog
10.Use the Data/Matrix Editor
( O 6 3 ) to create a new
data variable named errorlog.
11.In this new data variable,
define the c1, c2, and c3
column headers to refer to
data in rklog and eulerlog.
Also, enter column titles as
shown.
To define a column header,
move the cursor to that
column, press †, type the
reference expression (such
as rklog[1] for c1), and press
¸.
12.In the Data/Matrix Editor,
press „. Then press ƒand
define Plot 1 for the RK data,
as shown to the right.
13.Define Plot 2 for the Euler
data. Use the values shown
to the right.
Plot Type=xyline
Mark=Cross
x=c1
y=c3
14.Return to the Y= Editor,
press 3, and set
Graph = FUNCTION.
15.The exact solution to the
differential equation is given
below. Enter it as y1.
y1 = (100ùe^(x/10))/(e^(x/10)+9)
Note:
errorlog
lets you
combine the data in
rklog
and
eulerlog
so that you can
view the two sets of data
side by side.
Note:
rklog[1]
and
rklog[2]
refer to column 1 and 2 in
rklog
, respectively. Likewise
with
eulerlog[2]
.
Tip: Scroll through the data
variable to see how the RK
and Euler values differ for
the same time value.
Note: To see how to use
deSolve()
to find this exact,
general solution, refer to
page 196.
c3=
eulerlog[2]
c2=rklog[2]
c1=rklog[1] or
c1=eulerlog[1]
You can use C to scroll up to see
Plot 1 and Plot 2.