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
N1), 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
N1) but not u(
n
N2)).
• 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
N1) 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
N1) 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