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Sequence Graphing 6-11
8306SEQN.DOC TI-83 international English Bob Fedorisko Revised: 02/19/01 12:22 PM Printed: 02/19/01 1:36
PM Page 11 of 16
To select Web axes format, press
y
[
FORMAT
]
~
Í
. A
web plot graphs
u(
n
) versus u(
n
N
1)
, which you can use to
study long-term behavior (convergence, divergence, or
oscillation) of a recursive sequence. You can see how the
sequence may change behavior as its initial value changes.
When
Web axes format is selected, a sequence will not
graph properly or will generate an error.
•
It must be recursive with only one recursion level
(
u(
n
N
1)
but not u(
n
N
2)
).
•
It cannot reference
n
directly.
•
It cannot reference any defined sequence except itself.
In
Web format, press
s
to display the graph screen.
The TI
-
83:
•
Draws a
y=x
reference line in AxesOn format.
•
Plots the selected sequences with
u(
n
N
1)
as the
independent variable.
Note:
A potential convergence point occurs whenever a sequence
intersects the y=x reference line. However, the sequence may or may
not actually converge at that point, depending on the sequence’s initial
value.
To activate the trace cursor, press
r
. The screen
displays the sequence and the current
n
, X, and Y values (X
represents u(
n
N
1)
and Y represents u(
n
)). Press
~
repeatedly to draw the web step by step, starting at
n
Min.
In
Web format, the trace cursor follows this course.
1. It starts on the x-axis at the initial value
u(
n
Min) (when
PlotStart=1).
2. It moves vertically (up or down) to the sequence.
3. It moves horizontally to the
y=x
reference line.
4. It repeats this vertical and horizontal movement as you
continue to press
~
.
Graphing Web Plots
Graphing a Web
Plot
Valid Functions
for Web Plots
Displaying the
Graph Screen
Drawing the Web