Texas Instruments PLUS TI-89 - Manual (Page 79)

62 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 62 of 24
When Exact/Approx = APPROXIMATE , the TI -89 / TI-92 Plus converts
rational numbers and irrational constants to floating-point. However,
there are exceptions:
¦ Certain built-in functions that expect one of their arguments to be
an integer will convert that number to an integer if possible. For
example: d
(y(x), x, 2.0) transforms to d (y(x), x, 2) .
¦ Whole-number floating-point exponents are converted to integers.
For example:
x 2.0 transforms to x 2 even in the APPROXIMATE
setting.
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.
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.
If you do not plan to use
symbolic computations,
approximate results are
similar to familiar,
traditional numeric
calculators.
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 1.23457 E -11 .
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 .
APPROXIMATE
Setting