Texas Instruments PLUS TI-89 - Manual (Page 308)

Chapter 17: Programming 291
17PROGRM.DOC TI-89/TI-92 Plus: Programming (English) Susan Gullord Revised: 02/23/01 1:14 PM Printed: 02/23/01 2:18 PM Page 291 of 40
If you want a function or program to perform symbolic calculations,
you must use a global variable instead of a local. However, you must
be certain that the global variable does not already exist outside of
the program. The following methods can help.
¦ Refer to a global variable name, typically with two or more
characters, that is not likely to exist outside of the function or
program.
¦ Include DelVar within the function or program to delete the global
variable, if it exists, before referring to it. ( DelVar does not delete
locked or archived variables.)
To Perform
Symbolic
Calculations