140 Chapter 9: Sequence Graphing
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 140 of 14
Steps
³
TI-89
Keystrokes
›
TI-92 Plus
Keystrokes Display
1. Display the
MODE dialog box.
For Graph mode, select
SEQUENCE.
3
B4
¸
3
B4
¸
2. Display and clear the Y= Editor.
Then define the sequence as
u1(n) = iPart(.8ùu1(nì1)+1000).
Use
iPart
to take the integer part of
the result. No fractional trees are
harvested.
To access
iPart(
, you can use
2I
, simply type it, or
select it
from the CATALOG
.
¥#
ƒ8¸
¸
2I14
.8jU1c
jN|1d«
1000d¸
¥#
ƒ8¸
¸
2I14
.8U1c
N|1d«
1000d¸
3. Define
ui1 as the initial value
that will be used as the first
term.
¸
4000¸
¸
4000¸
4. Display the Window Editor. Set
the n and plot Window variables.
nmin=0 and nmax=50 evaluate the
size of the forest over 50 years.
¥$
0D50D
1D1D
¥$
0D50D
1D1D
5. Set the
x and y Window variables
to appropriate values for this
example.
0D50D
10D0D
6000D
1000
0D50D
10D0D
6000D
1000
6. Display the Graph screen. ¥% ¥%
7. Select
Trace. Move the cursor to
trace year by year. How many
years (nc) does it take the
number of trees (yc) to stabilize?
Trace begins at nc=0.
nc is the number of years.
xc = nc since n is plotted on the x
axis.
yc = u1(n), the number of trees at
year n.
…
Band A
as necessary
…
Band A
as necessary
Preview of Sequence Graphing
A small forest contains 4000 trees. Each year, 20% of the trees will be harvested (with 80%
remaining) and 1000 new trees will be planted. Using a sequence, calculate the number of
trees in the forest at the end of each year. Does it stabilize at a certain number?
Initially After 1 Year After 2 Years After 3 Years . . .
4000 .8 x 4000
+ 1000 .8 x (.8 x 4000 + 1000)
+ 1000 .8 x (.8 x (.8 x 4000 + 1000) + 1000)
+ 1000 . . .
By default, sequences use
the Square display style.