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Figure B-1. Displaying the Current Estimates During a
Numerical Calculation.
CALCULATING ...
AP1:3.19258240357
AP1: 0. 07000000000
DIII1:Ili
Sign of
+
}
LEFT
-
RIGHT for
each estimate
Since calculators cannot do calculations with infinite precision (the
HP -18C uses 12 digits in its
calculations),
sometimes the solver will be
un
able to find an estimate where LEFT
-
RIGHT is exactly
o.
How-
ever, the solver can distinguish between situations where the current
estimate
may be a solution, and situations where the solver cannot
find a
solution.
The search for a numerical solution can sometimes take several min-
utes.
(You can halt the search at any time by pressing any key.) There
are four possible outcomes for a numerical
solution:
• Case 1:
The HP-18C displays an answer on line 3 and there is no
message in lines 1 and
2.
It
is very likely that the answer on line 3
is a solution for the unknown variable.
There are two situations in which the solver returns a case 1 an-
swer (see figure B-2):
• Case
1a:
LEFT-RIGHT is exactly O
.
• Case 1
b:
LEFT - RIGHT is not zero for either
estimate.
However,
the solver has found two estimates that cannot get any closer
together. (Numbers that are as close together as possible are
called "neighbors.") Furthermore, LEFT
-
RIGHT is a positive
value for one estimate and a negative value for the other
estimate.
174
B: More About HP-18C Calculations
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