Texas Instruments TI-89 Titanium User Manual page 244

Enter
Note: ln(x y)
†
named xy.
L1
Because sin (sin(
q
expression is not simplified.
With a constraint, the expression can be simplified.
For ‚ or , press 8 Ã or 8 Â. You can also use 2 I
Note:
select them from a menu.
Using Substitutions vs. Defining a Variable
In many cases, you can achieve the same
effect as a substitution by defining the
variable.
However, substitution is preferable for most cases because the variable is defined only
for the current calculation and does not accidentally affect later calculations.
Substituting x=1 does not affect the next
calculation.
Symbolic Manipulation
instead of ; otherwise, xy is interpreted as a single variable
ln(xy)
)) = is not always valid, the
q
or 2 G
to
8 2
241