Texas Instruments PLUS TI-89 - Manual (Page 166)

Chapter 9: Sequence Graphing 149
09SEQUEN.DOC TI-89/TI-92 Plus: Sequence Graphing (English) Susan Gullord Revised: 02/23/01 10:59 AM Printed: 02/23/01 2:14 PM Page 149 of 14
5. On the Y= Editor, set Axes = WEB and Build Web = AUTO .
6. On the Window Editor, change
the Window variables.
nmin=0. xmin= ë 10. ymin= ë 10.
nmax=10. xmax=10. ymax=10.
plotStrt=1. xscl=1. yscl=1.
plotStep=1.
7. Regraph the sequence.
The web plot shows how
quickly the sequence
diverges to large negative
values.
This example shows how the initial value can affect a sequence.
1. On the Y= Editor ( ¥ # ), use the same sequence defined in the
divergence example: u1(n) = 3.2u1(n м 1) м .8(u1(n ì 1)) 2 . Set initial
value ui1 = 0.5 .
2. Set Axes = TIME .
3. On the Window Editor
( ¥ $ ), set the
Window variables.
nmin=1. xmin=0. ymin=0.
nmax=100. xmax=100. ymax=5.
plotStrt=1. xscl=10. yscl=1.
plotStep=1.
4. Graph the sequence
( ¥ %).
5. On the Y= Editor, set Axes = WEB and Build Web = AUTO .
6. On the Window Editor, change
the Window variables.
nmin=1. xmin= ë 2.68 ymin= ë 4.7
nmax=100. xmax=6.47 ymax=4.7
plotStrt=1. xscl=1. yscl=1.
plotStep=1.
7. Regraph the sequence.
8. Press …. Then use B to trace the web.
As you trace to larger values of nc , notice that xc and yc oscillate
between 2.05218 and 3.19782 .
9. On the Window Editor, set
plotstrt=50 . Then regraph the
sequence.
Example:
Oscillation
Note: Compare this graph
with the divergence
example. This is the same
sequence with a different
initial value.
Note: The web moves to an
orbit oscillating between two
stable points.
Note: By starting the web
plot at a later term, the
stable oscillation orbit is
shown more clearly.
u(n)
y=x
u(n ì 1)
u(n)
n
u(n)
y=x
u(n ì 1)
y=3.2x ì .8x ñ
y=3.2x ì .8x с