Creating And Evaluating User-Defined Functions - Texas Instruments TI-89 Manual Book

Creating and Evaluating User-Defined Functions

Format of a
Function
Note: Function names
follow the same rules as
variable names. Refer to
"Storing and Recalling
Variable Values" in
Chapter 2.
Creating a User-
Defined Function
User-defined functions can be a great time-saver when you
need to repeat the same expression (but with different values)
multiple times. User-defined functions can also extend your
capabilities beyond the built-in functions.
TI-89 / TI-92 Plus's
The following examples show user-defined functions with one
argument and two arguments. You can use as many arguments as
necessary. In these examples, the definition consists of a single
expression (or statement).
3
cube(x) = x
Definition
Argument list
Function name
When defining functions and programs, use unique names for
arguments that will not be used in the arguments for a subsequent
function or program call.
In the argument list, be sure to use the same arguments that are used
in the definition. For example,
when you evaluate the function.
Arguments ( and in these examples) are placeholders that
x y
represent whatever values you pass to the function. They do not
represent the variables
the arguments when you evaluate the function.
Use one of the following methods.
Method Description
§
Store an expression to a function name
(including the argument list).
command Define a function name (including the argument
Define
list) as an expression.
Program Editor Refer to Chapter 17 for information on creating a
user-defined function.
Chapter 5: Additional Home Screen Topics
xroot(x,y) = y
Function name
gives unexpected results
cube(n) = xò
and unless you specifically pass
x y
1
x
Definition
Argument list
and as
x y
97