Equation library  Hewlett Packard
This is a discussion on Equation library  Hewlett Packard ; The equation library included in the hp 50g is really useful and
helpful. However, I'm encountering some problems with the equation
concerning the "thin lenses" (or the one concerning "spherical
reflecion", which is the same). When I solve the equation ...

Equation library
The equation library included in the hp 50g is really useful and
helpful. However, I'm encountering some problems with the equation
concerning the "thin lenses" (or the one concerning "spherical
reflecion", which is the same). When I solve the equation using the
numeric solver, and i choose negative values for some vars (for
example, negative value of the focal length), the calculation results
in two possible errors:
1) a message is displayed, saying that no solution could be found;
2) (more frequently) the solution is the biggest number the calculator
can disaply (9.999e499).
As the equation is not so difficult to solve, I wonder why the numeric
solver doesn't manage to solve it.
Giovanni

Re: Equation library
Because it was ported rather hastily ?
You might want to consider the use of an alternative EQNLIB, some are
available on hpcalc.org or give my TreeBrowser a try. A demo version
(in English and German) is available on my website http://www.software49g.gmxhome.de.
It is
also possible to create your own libraries of equations with it
easily.
Greetings
Andreas
On 6 Apr., 21:29, "Giovanni" wrote:
> The equation library included in the hp 50g is really useful and
> helpful. However, I'm encountering some problems with the equation
> concerning the "thin lenses" (or the one concerning "spherical
> reflecion", which is the same). When I solve the equation using the
> numeric solver, and i choose negative values for some vars (for
> example, negative value of the focal length), the calculation results
> in two possible errors:
> 1) a message is displayed, saying that no solution could be found;
> 2) (more frequently) the solution is the biggest number the calculator
> can disaply (9.999e499).
> As the equation is not so difficult to solve, I wonder why the numeric
> solver doesn't manage to solve it.
>
> Giovanni

Re: Equation library
On Fri, 06 Apr 2007 14:29:26 0500, Giovanni wrote:
> The equation library included in the hp 50g is really useful and
> helpful. However, I'm encountering some problems with the equation
> concerning the "thin lenses" (or the one concerning "spherical
> reflecion", which is the same). When I solve the equation using the
> numeric solver, and i choose negative values for some vars (for
> example, negative value of the focal length), the calculation results
> in two possible errors:
> 1) a message is displayed, saying that no solution could be found;
> 2) (more frequently) the solution is the biggest number the calculator
> can disaply (9.999e499).
> As the equation is not so difficult to solve, I wonder why the numeric
> solver doesn't manage to solve it.
The *numeric* solver does not "solve" equations;
it merely tries existing numeric guesses for the variable
to be calculated, then heads in whatever direction
seems to reduce the difference between the value of
left and right sides of the equation.
To obtain a useful answer therefore requires:
o Existence of a solution.
o Supplying feasible initial guess(es).
Example: 'INV(X)=1' STEQ 0 'X' STO 30 MENU
If you try solving for X without supplying another guess,
it will head toward +infinity and stop at 9.99999999999E499
If you first store 5 into 'X' and try again,
the solution X=1 will promptly be found.
Although this equation is rather trivial to solve
*algebraically*, the *numeric* solver does not use algebra;
it is therefore able to get numerical answers even for equations
that are algebraically intractible, but there is a small price
to pay for "blind searching" via only "closer" vs. "farther"
as clues, which is that you have to put the target within reach
to begin with, and start searching in the right general direction.
[r>] [OFF]

Re: Equation library
On 6 Apr, 22:48, "John H Meyers" wrote:
> On Fri, 06 Apr 2007 14:29:26 0500, Giovanni wrote:
> > The equation library included in the hp 50g is really useful and
> > helpful. However, I'm encountering some problems with the equation
> > concerning the "thin lenses" (or the one concerning "spherical
> > reflecion", which is the same). When I solve the equation using the
> > numeric solver, and i choose negative values for some vars (for
> > example, negative value of the focal length), the calculation results
> > in two possible errors:
> > 1) a message is displayed, saying that no solution could be found;
> > 2) (more frequently) the solution is the biggest number the calculator
> > can disaply (9.999e499).
> > As the equation is not so difficult to solve, I wonder why the numeric
> > solver doesn't manage to solve it.
>
> The *numeric* solver does not "solve" equations;
> it merely tries existing numeric guesses for the variable
> to be calculated, then heads in whatever direction
> seems to reduce the difference between the value of
> left and right sides of the equation.
>
> To obtain a useful answer therefore requires:
>
> o Existence of a solution.
>
> o Supplying feasible initial guess(es).
>
> Example: 'INV(X)=1' STEQ 0 'X' STO 30 MENU
>
> If you try solving for X without supplying another guess,
> it will head toward +infinity and stop at 9.99999999999E499
>
> If you first store 5 into 'X' and try again,
> the solution X=1 will promptly be found.
>
> Although this equation is rather trivial to solve
> *algebraically*, the *numeric* solver does not use algebra;
> it is therefore able to get numerical answers even for equations
> that are algebraically intractible, but there is a small price
> to pay for "blind searching" via only "closer" vs. "farther"
> as clues, which is that you have to put the target within reach
> to begin with, and start searching in the right general direction.
>
> [r>] [OFF]
So, the numeric solver is the same as the one which can be found on
the HP 33s, I see...
Thnak you so much for helping me!
Giovanni

Re: Equation library
Giovanni wrote:
> The equation library included in the hp 50g is really useful and
> helpful. However, I'm encountering some problems with the equation
> concerning the "thin lenses" (or the one concerning "spherical
> reflecion", which is the same). When I solve the equation using the
> numeric solver, and i choose negative values for some vars (for
> example, negative value of the focal length), the calculation results
> in two possible errors:
> 1) a message is displayed, saying that no solution could be found;
> 2) (more frequently) the solution is the biggest number the calculator
> can disaply (9.999e499).
> As the equation is not so difficult to solve, I wonder why the numeric
> solver doesn't manage to solve it.
Try starting the Equation Library while being in approximate mode, see
how it goes.
JY