Symbolic csgn removal

[schneidrax]

Both r and n(r) are real and positive. Is there a better way to remove the symbolic csgn function?

[ptc-1368288]

On 10/19/2009 11:35:18 AM, schneidrax wrote:
>Both r and n(r) are real and
>positive. Is there a better
>way to remove the symbolic
>csgn function?
>
>________________________________

That would be disaster if you mean remove from the symbolic. It is a simple but scalar math function and as such enables many functions to have their full mathematical scalar meaning. Would you also remove sgn ?

jmG

[PhilipOakley]

So you need a way of saying: assume n(r) > 0
Philip Oakley

[schneidrax]

On 10/19/2009 4:32:02 PM, philipoakley wrote:
>So you need a way of saying:
>assume n(r) > 0
>Philip Oakley

Yep.

[AlvaroDíaz]

On 10/19/2009 4:52:44 PM, schneidrax wrote:
>On 10/19/2009 4:32:02 PM, philipoakley
>wrote:
>>So you need a way of saying:
>>assume n(r) > 0
>>Philip Oakley
>
>Yep.

The maple way is algsubs, but hard to access from mathcad. Try the last simplify, but use with careful the symbolic keyword.



Regards. Alvaro.

[schneidrax]

Thanks, Alvaro. Works like a charm.

[ptc-1368288]

On 10/19/2009 8:23:50 PM, schneidrax wrote:
>Thanks, Alvaro. Works like a charm.
_______________________

You can attack more efficiently in the sense of csgn(z)
Why do you call the built-in 'z', why do you call 'x' ?
... z as reserved to the complex domain,
universally by the "mathematical community" ?



jmG

[TomGutman]

Whst version of Mathcad? It's better to post actual Mathcad files than just pictures. I don't really like retyping a lot of things -- I make too many errors that way.

Generally when working with the symbolic processor I just don't use the function notation. Even if n is a function of r I leave it as just n rather than n(r). Then there is no problem assuming n>0.

This fails to differentiate properly using the standard differentiation operator, but I either use subst to restore the explicit functional notation first, or (more commonly) use the TotDeriv function from my Jacobian etc. worksheet.
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� � � � Tom Gutman