Texas Instruments TITANIUM TI-89 - Manual (Page 270)

Symbolic Manipulation 270
For Information about Creating a User-Defined Function For Information about Creating a User-Defined Function For Information about Creating a User-Defined Function For Information about Creating a User-Defined Function
Refer to:
• “Creating and Evaluating User-Defined Functions” in the Calculator Home Screen
module.
• “Graphing a Function Defined on the Home Screen” and “Graphing a Piecewise
Defined Function” in the Calculator Home Screen module.
• “Overview of Entering a Function” in the Programming module.
Undefined Functions Undefined Functions Undefined Functions Undefined Functions
You can use functions such as f(x) , g(t) , r( q ) , etc., that have not been assigned a
definition. These “undefined” functions yield symbolic results. For example:
Single-Statement Functions Single-Statement Functions Single-Statement Functions Single-Statement Functions
You can use user-defined functions consisting of a single expression. For example:
Use DelVar to ensure that f(x) and g(x) are not
defined.
Then find the derivative of f(x) g(x) with
respect to x.
Note: To select d from the Calc toolbar menu,
press … 1 (or press 2 = on the keyboard).