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Reversing' a function...

Desiv5-disabled
1-Newbie

Reversing' a function...

Hello,

I have, let's say a function
S(F,L,d):= 32*F*L/(pi*d^3)
Is it possible for Mathcad to calculate (symbolic) the function d(S,F,L)?

Thanks in advance!
7 REPLIES 7

Because the expression is cubic in d, there are three answers:


Fred Kohlhepp
fkohlhepp@sikorsky.com

Yeap, that's what I need.

Thank you a lot!

On 10/22/2009 8:25:41 AM, Desiv5 wrote:
>Yeap, that's what I need.
>
>Thank you a lot!
_______________________________

My interpretation is much different. In mathematics, inversing a function is solving for this function ... a largely unsuccessful task unless you are equipped with a solid symbolic engine like Maple. In Mathcad 11.2a [the Maple version], NOT ONE inversion has ever failed and there is a procedure for that and several work sheets. No problem solving at random, but the "solving function" is lot more interesting ! Hope you understand my additional input.
"Reversing a function" does not belong to mathematics.

jmG
ELSID
4-Participant
(To:ptc-1368288)

Can anyone tell me what this error means (from jmG's sheet)

On 10/22/2009 11:51:24 AM, ElSid wrote:
>Can anyone tell me what this
>error means (from jmG's sheet)
_______________________________

Can't help, specific to version 14. For that particular case, take the first solution from Fred, plug in U(d) and adapt, use the cubic root symbol.



jmG

Essentially a bug. A mistake on the part of the Mathcad developers who got confused between the four argument form of root, which is inherently a numeric algorithm, and the two argument form of root, which can be interpeted either numerically or symbolically.

The solution is not to attempt symbolic evaluation of root at all, but rather use the symbolic solve keyword directly.
__________________
� � � � Tom Gutman

>Essentially a bug<<br> ___________________

That makes it clear, and with such a bug, even if it could interpret the symbolic call ... then it won't. This kind of bug is damned serious. The other aspect is if MuPad has insufficient algebraic solve, which in that case the error message should state something like "Not a valid symbolic".

jmG
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