Texas Instruments TI-89 Manual page 6

Chapter 1
1.1 Models, Functions, and Graphs
There are many uses for a function that is entered in the calculator. One of the ways we often
use functions is to graph them in an appropriate viewing windows. Because you must enter a
function on one line (that is, you cannot type fractions and exponents the same way you write
them on paper even though the TI-89 displays them in this form after they are entered), it is very
important to have a good understanding of the calculator's order of operations and to correctly
use parentheses whenever they are needed.
1.1.1 ENTERI NG AN EQUATI ON I N THE GRAPHI NG LI ST The graphing list contains
space for 99 equations, and the output variables are called by the names
When you want to graph an equation, first enter in the graphing list. You must use
.
y 9 9 ( x ) =
as the input variable if you intend to draw the graph of the equation or use the TI-89 table.
We illustrate graphing with the equation in Example 4 of Section 1.1: v(t) = 3.622(1.093
Press either
graphing list. If there are any previously entered equations that
you will no longer use, delete them from the graphing list. For
convenience, we use the first, or
We intend to graph this equation, so the input variable must be
called x, not t. Enter the right-hand side of the equation,
3.622(1.093 x ), with
Note that you must use the
key), not the times sign key,
CAUTI ON: Press
These are the data plots that we will not use until Section 1.5. None of these plots should have a
check mark to the left of the name when you are graphing an equation and not graphing data
points. If any of these has a check mark, use
to make the check mark go away. Otherwise, you may receive an error message.
F4 [ ]
b
DEFI NI NG A FUNCTI ON ON THE HOME SCREEN
graphing list or defined on the home screen. We illustrate both of these methods, and you can
use the one you prefer. Press
Type in v(t) = 3.622(1.093
0 (V) ( ) = 3 . 6 2 2 ( 1 . 0 9 3 ^
T
On the home screen, any letter can be used for the variable.
Note that if you prefer, you can enter the equation with x instead
of t as the input variable. (The TI-89 now knows this function
by two names:
Copyright © Houghton Mifflin Company. All rights reserved.
I ngredients of Change:
Functions and Linear Models
or
F1 (Y ) APPS 2 [Y= Editor]
=
, location in the graphing list.
y 1
3 . 6 2 2 ( 1 . 0 9 3 ^
key for x (under the
X
.
and notice the names
▲
2nd ESC (QUIT)
t
) with
F4 [Other] 1 [Define] alpha
and v.)
y 1
to access the
To delete an equation from
the Y
cursor on the line with the
equation. Press CLEAR .
) ENTER .
X
HOME
..., at the top of the
Plot 1, Plot 2, Plot 9
until the cursor is on the plot name and press
▲
Functions can be entered in the
or to return to the home screen.
HOME
) ENTER .
T
and
, , ...,
y 1 ( x ) = y 2 ( x ) =
x
t
).
list, position the
=
list.
Y=
TI 89-6