Chapter 3: Symbolic Manipulation 79
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 79 of 24
¦ Delete unneeded variables and/or Flash applications, particularly
large-sized ones.
− Use 2°
as described in Chapter 21 to view and
delete variables and/or Flash applications.
¦ On the Home screen:
− Clear the history area (ƒ 8) or delete unneeded history pairs.
− You can also use ƒ 9 to reduce the number of history pairs
that will be saved.
¦ Use 3 to set Exact/Approx = APPROXIMATE. (For results that have
a large number of digits, this uses less memory than AUTO or EXACT.
For results that have only a few digits, this uses more memory.)
¦ Split the problem into parts.
− Split solve(aùb=0,var ) into solve(a=0,var ) and solve(b=0,var ).
Solve each part and combine the results.
¦ If several undefined variables occur only in a certain
combination, replace that combination with a single variable.
− If m and c occur only as mùcñ, substitute e for mùcñ.
− In the expression
(a+b)ñ+ (a+b)ñ
1 ì(a+b)ñ , substitute c for (a+b) and
use
cñ+ cñ
1 ìcñ . In the solution, replace c with (a+b).
¦ For expressions combined over a common denominator, replace
sums in denominators with unique new undefined variables.
− In the expression x
añ+bñ + c + y
añ+bñ + c , substitute d for
añ+bñ + c and use x
d + y
d . In the solution, replace d with
añ+bñ + c.
¦ Substitute known numeric values for undefined variables at an
earlier stage, particularly if they are simple integers or fractions.
¦ Reformulate a problem to avoid fractional powers.
¦ Omit relatively small terms to find an approximation.
If You Get an Out-of-Memory Error
The TI-89 / TI-92 Plus stores intermediate results in memory and
then deletes them when the calculation is complete. Depending
on the complexity of the calculation, the TI-89 / TI-92 Plus may run
out of memory before a result can be calculated.
Freeing Up Memory
Simplifying
Problems