The chances are that one will have a ‘+’ symbol to the left of it, while the other has a ‘-‘. This is telling you that
the ‘+’ value is greater than required, while the ‘-‘ value is smaller. As you watch you should see the two
values converge to the true answer.
But is it? The true answer is actually
3
3000
, as is shown right in the hp
40gs CAS. Unless you were alert enough to spot it you probably would
not realize that the value supplied was a cube root.
On most calculators there is no way to obtain this exact answer because
the calculator doesn’t use algebra.
However, the CAS or Computer Algebra System
on the hp 40gs
does
use algebra! As you can
see in the screen shots to the right, the CAS on
the hp 40gs is perfectly capable of giving you
the algebraically correct answer, and it does it
by following the same rules that you do.
The HP CAS system was created by Bernard Parisse,
Université de Grenoble, for the HP 49g calculator. It was
improved and adapted for inclusion on the HP 40g with the help
of Renée De Graeve, Jean-Yves Avenard and Jean Tavenas, and
again adapted for inclusion in the HP49g+, HP48GII and HP 40gs
calculators. The HP CAS system offers the user a vast array of functions
and abilities as well as an easy user interface which displays equations
as they appear on the page.
It will let you perform virtually any mathematical manipulation you might
need.
For an example of the fundamental difference between
working in the CAS, with its exact mode & infinite
precision, and working in the normal
HOME
view, in
approximate mode with 10
-12
precision, you need only
1
consider the two contrasting results of
ASIN(1)
and
×
9
9
shown to the right as they appear in the
HOME
view and in the
CAS.
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