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68 Chapter 3: Symbolic Manipulation
03SYMBOL.DOC TI-89/TI-92 Plus: Symbolic Manipulation (English) Susan Gullord Revised: 02/23/01 10:52 AM Printed: 02/23/01 2:12 PM Page 68 of 24
¦
Substitution occurs only
where there is an
exact
match for the substitution.
¦ Infinite recursions can occur when you define a substitution
variable in terms of itself.
sin(x)|x=x+1
When you enter a substitution that causes an infinite recursion:
− An error message is
displayed.
− When you press
N
, an
error is shown in the
history area.
¦ 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.
− As a general rule, you
should substitute for a
single variable.
− Substituting for more
general expressions
(either
m
ø
c
ñ
=e
or
c
ñø
m=e
) may not work
as you anticipate.
Be Aware of the
Limitations of
Substitutions
Tip: Use the solve function
to help determine the single-
variable substitution.
Only x
2
was replaced, not x
4
.
Define the substitution in
simpler terms for a more
complete substitution.
Substitutes sin(x+1), sin(x+1+1), sin(x+1+1+1), etc.
No match for substitution