Texas Instruments TITANIUM TI-89 - Manual (Page 242)

Symbolic Manipulation 242
Functions such as solve and ‰ (integrate) can use both exact symbolic and approximate
numeric techniques. These functions skip all or some of their exact symbolic techniques
in the APPROXIMATE setting.
AUTO Setting AUTO Setting AUTO Setting AUTO Setting
When Exact/Approx = AUTO, the handheld uses exact rational arithmetic wherever all of
the operands are rational numbers. Otherwise, floating-point arithmetic is used after
Advantages Disadvantages
If exact results are not needed, this
might save time and/or use less
memory than the EXACT setting.
Approximate results are sometimes
more compact and comprehensible
than exact results. Results with undefined variables or
functions often exhibit incomplete
cancellation. For example, a
coefficient that should be 0 might be
displayed as a small magnitude such
as 1.23457E
- 11.
If you do not plan to use symbolic
computations, approximate results
are similar to familiar, traditional
numeric calculators. Symbolic operations such as limits
and integration are less likely to give
satisfying results in the
APPROXIMATE setting.
Approximate results are sometimes
less compact and comprehensible
than exact results. For example, you
may prefer to see 1/7 instead of
.142857.