Chapter 11: Differential Equation Graphing 195
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 195 of 26
16.In the Window Editor, set
the Window variables.
xmin=ë10. ymin=ë10. xres=2.
xmax=100. ymax=120.
xscl=10. yscl=10.
17.Display the Graph screen
( ¥%).
18.In the Window Editor, set the
Window variables to zoom in
so that you can examine the
differences in more detail.
xmin=39.7 ymin=85.5 xres=2.
xmax=40.3 ymax=86.
xscl=.1 yscl=.1
19.Return to the Graph screen.
20.Press …to trace, and then
press Cor Duntil y1 is
selected. (1 shows in upper
right corner.) Then enter 40.
By moving the trace cursor to trace each solution to xc = 40, you can
find that:
¦ The exact solution (y1) is 85.8486, rounded to six digits.
¦ The RK solution (Plot 1) is 85.8952.
¦ The Euler solution (Plot 2) is 85.6527.
You can also use the Data/Matrix Editor to open the errorlog data
variable and scroll to time = 40.
Note: The fuzzy line on the
graph indicates differences
between the RK and Euler
values.
y1 is selected when 1 shows here.
Euler (Plot 2)
RK (Plot 1)
Exact solution (y1)