Texas Instruments Titanium TI-89 User Manual

Symbolic Manipulation 236
Determining If a Variable Is Exists
Determining If a Variable Is ExistsDetermining If a Variable Is Exists
Determining If a Variable Is Exists
• If x is defined, the result may be in a form
you did not expect.
Note: When defining a variable, it’s a good
practice to use more than one character
in the name. Leave one-character names
undefined for symbolic calculations.
Method: Example:
Enter the variable name.
Use the
isVar() function.
Unless you knew that
5 had been stored to
x previously, the
answer 75 could be
misleading.
If defined, the variable’s
value is displayed.
If undefined, the variable
name is displayed.
If defined, “true” is
displayed.
If undefined, “false” is
displayed.

Texas Instruments Titanium TI-89 Specifications

General

Display Type	LCD
Display Resolution	160 x 100 pixels
Memory	188 KB RAM, 2.7 MB Flash ROM
Type	Graphing Calculator
Display	Monochrome
Processor	Motorola 68000
Processor Speed	12 MHz
Power Source	4 AAA batteries
Connectivity	USB
Programming	TI-BASIC, Assembly
Operating System	AMS (Advanced Mathematics Software)