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From: John H Meyers on 28 Mar 2010 21:58
On 3/28/2010 7:38 PM, radw wrote:

> What would happen if you made 's' the independent variable?
> I did and I get the memory error even when all memory is clear.

No problem when I did 's' STOVX before what I previously posted,
provided that no variable named 's' exists.

[r->] [OFF]
From: asparnique on 29 Mar 2010 02:57

"John H Meyers" <jhmeyers(a)nomail.invalid> wrote in message
news:4BB00929.3040302(a)nomail.invalid...
> On 3/28/2010 7:38 PM, radw wrote:
>
>> What would happen if you made 's' the independent variable?
>> I did and I get the memory error even when all memory is clear.
>
> No problem when I did 's' STOVX before what I previously posted,
> provided that no variable named 's' exists.
>
> [r->] [OFF]
>

Ahhh yes silly me, still getting used to the memory on the 50G, yes in fact
it appears there was enough memory, but I may have had a variable named 's'
from a previous calculation. Effectively after having deleted a whole lot of
other stuff I may have also deleted this 's' and so it all worked fine after
that. Therefore no memory problem probably...

However does that mean I cannot set 's' as the independent variable in CAS ?
or just that I cannot have that, and also another 's' that is used for
storage ? If that is the case, then the same error would have occurred if I
would have had 'x' used as storage, is that correct ??

Cheers, M


From: John H Meyers on 29 Mar 2010 05:08
On 3/29/2010 1:57 AM, asparnique wrote:

> Does that mean I cannot set 's' as the independent variable in CAS ?
> or just that I cannot have that, and also another 's'
> that is used for storage ?
>
> If that is the case, then the same error would have occurred
> if I would have had 'x' used as storage, is that correct ??

The CAS is incapable of performing certain functions
(e.g. derivative, integral, solve) if a variable exists,
either in the same or any higher directory,
having the same name as the principal variable
involved in the operation to be performed.

That's why the CAS will often demand that you purge
any such variable(s), before it will perform an operation.

This is a kind of flaw, but that's the way it is.

There is a kind of "helper" that can be used
to "hide" any such variable(s) that you want to keep,
during the execution of any CAS command(s),
if being forced to purge your variable(s) is irksome:
http://www.hpcalc.org/search.php?query=xc49

In the case of your particular PARTFRAC example, however,
it seemed to work fine, after CASCFG, as long as RCLVX RCL
produces an "Undefined Name" error, even if other variables exist,
including the variable 's' itself -- it's a bit safer, however,
in general, not to try to fool the CAS by lying about which variable
is particularly significant to various operations,
since the CAS might then lie right back to you, in its answer :)

[r->] [OFF]
From: radw on 29 Mar 2010 21:02
On Mar 29, 5:08 am, John H Meyers <jhmey...(a)nomail.invalid> wrote:
> On 3/29/2010 1:57 AM, asparnique wrote:
>
> > Does that mean I cannot set 's' as the independent variable in CAS ?
> > or just that I cannot have that, and also another 's'
> > that is used for storage ?
>
> > If that is the case, then the same error would have occurred
> > if I would have had 'x' used as storage, is that correct ??
>
> The CAS is incapable of performing certain functions
> (e.g. derivative, integral, solve) if a variable exists,
> either in the same or any higher directory,
> having the same name as the principal variable
> involved in the operation to be performed.
>
> That's why the CAS will often demand that you purge
> any such variable(s), before it will perform an operation.
>
> This is a kind of flaw, but that's the way it is.
>
> There is a kind of "helper" that can be used
> to "hide" any such variable(s) that you want to keep,
> during the execution of any CAS command(s),
> if being forced to purge your variable(s) is irksome:http://www.hpcalc.org/search.php?query=xc49
>
> In the case of your particular PARTFRAC example, however,
> it seemed to work fine, after CASCFG, as long as RCLVX RCL
> produces an "Undefined Name" error, even if other variables exist,
> including the variable 's' itself -- it's a bit safer, however,
> in general, not to try to fool the CAS by lying about which variable
> is particularly significant to various operations,
> since the CAS might then lie right back to you, in its answer :)
>
> [r->] [OFF]

John, thanks for the insight, as always your responses are very
thorough. I installed XC followed the examples and still get an error
message when ever I select the independent variable. I'll have to
spend some more time trying to figure out what I'm doing wrong this
weekend. I get the solution as long as I don't use the independent
variable.

I made some additional observations using the independent variable and
if I simplelied the problem to 'A/((X^2 + B*X + C)*(X^2 + D*X + C))' I
would get the following answer
'-((A*D-A*ƒ-(4*C-D^2))/(-(C*ƒ-(4*C-D^2)*B)+D*C*ƒ-(4*C-D^2))/(2*X+(D+ƒ-
(4*C-D^2))))+(A*B^2-4*A*C+A*B*ƒ(B^2-4*C))/(C*B^3-D*C*B^2-4*C^2*B
+4*D*C^2)/(2*X+(B-ƒ(B^2-4*C)))-(-(A*B^2-4*A*C)+A*B*ƒ(B^2-4*C))/(C*B^3-
D*C*B^2-4*C^2*B+4*D*C^2)/(2*X+(B+ƒ(B^2-4*C)))+(A*D+A*ƒ-(4*C-D^2))/(-
(C*ƒ-(4*C-D^2)*B)+D*C*ƒ-(4*C-D^2))/(2*X+(D-ƒ-(4*C-D^2)))' where the
'ƒ' represents a squareroot symbol.

If I solve the complete problem with numerical values for the
coefficients '(12093/100000)/((X^2 + (73/200)*X + 99/200)*(X^2 +
(199/200)*X + 99/200)*(X^2 + (279/200)*X +99/200))' then I get the
solution
'-((806200*X+294263)/10395/(200*X^2+73*X+99))+(806200*X+802169)/10395/
(200*X^2+199*X+99)' which matches your solution except I'm using 'X'
vs 's'.

Ronald Williams
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