Texas Instruments TITANIUM TI-89 - Manual (Page 252)

Symbolic Manipulation 252
• Infinite recursions can occur when you define a substitution variable in terms of
itself.
When you enter a substitution that causes an infinite recursion:
• Internally, an expression is sorted according to the automatic simplification rules.
Therefore, products and sums may not match the order in which you entered them.
- An error message is displayed.
- When you press N, an error is
shown in the history area.
- As a general rule, you should
substitute for a single variable.
sin(x)|x=x+1
Substitutes sin(x+1), sin(x+1+1),
sin(x+1+1+1), etc