Texas Instruments TITANIUM TI-89 - Manual (Page 224)

Calculator Home Screen 224
Arguments (x and y in these examples) are placeholders that represent whatever values
you pass to the function. They do not represent the variables x and y unless you
specifically pass x and y as the arguments when you evaluate the function.
Creating a User-Defined Function Creating a User-Defined Function Creating a User-Defined Function Creating a User-Defined Function
Use one of the following methods.
Method Description
§ Store an expression to a function name (including
the argument list).
Define command Define a function name (including the argument
list) as an expression.
Program Editor Refer to Programming or information on creating a
user-defined function.