Texas Instruments Titanium TI-89, User Manual

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Calculator Home Screen 211
Creating and Evaluating User-Defined Functions
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 TI-89 Titanium’s capabilities beyond the built-in functions.
Format of a Function
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).
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.
Note:
Function names follow the same rules as variable names. Refer to “Storing and
Recalling Variable Values” in Operating the Calculator .
In the argument list, be sure to use the same arguments that are used in the definition.
For example,
cube(n) = x
3
gives unexpected results when you evaluate the function.
cube(x) = x
3
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Ê
Function name
Ë
Argument list
Ì
Definition
xroot(x,y) = y
1/x
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