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From: Colin Croft on 5 Dec 2007 22:42
I'm working with the CAS on the 40gs but I'd imagine that the same
things might apply with the 50g since the 40 CAS was a graft of the 49's...

I'm trying to solve SIN(X)=1/4*X+1/2 (which has three real solns when
graphed) but when I enter SOLVEVX(SIN(X)=1/4*X+1/2) into the CAS it says:

! SOLVEVX Error:
Not reducible to
a rational expression.

Can someone please tell me what this means and why it won't solve the
equation (and how to get it to do it)? I've tried different settings in
the MODES view (equivalent, I gather, to the 50g flags except there's a
very limited number of them) with no effect on the message. Changing to
SOLVE had no effect.

Also, when I looked in the manual under the SOLVE function it says, in
passing, that:

SOLVE also enables you to solve a system of non-linear
equations, if they are polynomials. (If they are not
polynomials, use MSOLV in the HOME screen to get a
numerical solution.)

I can't find any reference to MSOLV anywhere else in any manual, nor
does it appear on any menu so far as I can see. So.... huh?
From: TW on 5 Dec 2007 23:04
Not sure about the other as I've generally not understood that either.

> I can't find any reference to MSOLV anywhere else in any manual, nor
> does it appear on any menu so far as I can see. So.... huh?

Copy and paste strikes again! I'd guess the text was just pulled from
a 50 manual. MSOLV is not in the 39/40 AFAIK.

TW
From: Colin Croft on 5 Dec 2007 23:49
TW wrote:

> Not sure about the other as I've generally not understood that either.
>
>
>>I can't find any reference to MSOLV anywhere else in any manual, nor
>>does it appear on any menu so far as I can see. So.... huh?
>
>
> Copy and paste strikes again! I'd guess the text was just pulled from
> a 50 manual. MSOLV is not in the 39/40 AFAIK.
>
> TW


Ah. That explains it. Any ideas on the other issue?
From: hgabert on 6 Dec 2007 10:30
On Dec 5, 9:49 pm, Colin Croft <ccr...(a)removethis.hphomeview.com>
wrote:
> TW wrote:
> > Not sure about the other as I've generally not understood that either.
>
> >>I can't find any reference to MSOLV anywhere else in any manual, nor
> >>does it appear on any menu so far as I can see. So.... huh?
>
> > Copy and paste strikes again! I'd guess the text was just pulled from
> > a 50 manual. MSOLV is not in the 39/40 AFAIK.
>
> > TW
>
> Ah. That explains it. Any ideas on the other issue?

SOLVE and SOLVEVX weren't designed to solve general, irrational, or
even transcendental equations (if so, that would have been quite the
feat!).

So, the above equation has to be solved numerically for a specific
root. (But if this is any consolation, you can solve 'SIN(X)=1/2'
symbolically with SOLVEVX).
From: John H Meyers on 6 Dec 2007 10:38
On Wed, 05 Dec 2007 21:42:58 -0600, Colin Croft wrote:

> I'm working with the CAS on the 40gs but I'd imagine that the same
> things might apply with the 50g since the 40 CAS was a graft of the 49/50's...
>
> I'm trying to solve SIN(X)=1/4*X+1/2 (which has three real solns when
> graphed) but when I enter SOLVEVX(SIN(X)=1/4*X+1/2) into the CAS it says:
> ! SOLVEVX Error: Not reducible to a rational expression.

Are you expecting the CAS to automatically invoke a numeric solver,
and to produce all of the roots,
when no algebraic solution method exists?

To see why it can't, try writing a program to find ALL numeric roots
of ANY arbitrary equation.

The closest I can come to that still requires more input than given above:

ROOTS - search for numeric roots, given interval endpoints and a "step"
(with arguments similar to the SEQ command):
http://groups.google.com/group/comp.sys.hp48/msg/ce02637fba5af50f
http://www.hpcalc.org/search.php?query=allroots

Why it's difficult to do otherwise:
http://groups.google.com/group/comp.sys.hp48/msg/982a15b08f0aa792

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