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06-25-2013
06:07 PM

06-25-2013
06:07 PM

Any comment s appreciated,

Ray

Solved! Go to Solution.

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06-26-2013
07:05 AM

06-26-2013
07:05 AM

As Valery already pointed out the symbilc engine in MC14 and above is muPad, the engine in older versions was Maple, considered by many users as the better one.

muPads behaviour is sometiome annyoing, while mathematically perhaps more correct than that of Maple. Maple obviously is implicitely assuming that X and Y are real values as most of us would do, too, as the "formula" for calculating the absolute value you have in mind is valid for real X and Y only:

So if you want to assume X and Y as real values, you have to tell muPad explicitely so. Additionally you have to demand muPad you want it to simplify the expression.

Maple assumed by default variables and results to be real values and you could change that by using the modifier "complex".

muPad (unfortunately!?) defaults to "complex" and making it think "real" can be quite a challenge sometimes.

6 REPLIES 6

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06-26-2013
12:17 AM

06-26-2013
12:17 AM

Re: MathCAD 14 symbolic solver

It is an old problem.

Matcad 7 has the symbolic engine from Maple and Mathcad 13(?)-15 and Prime - from MuPAD.

Send pleade your sheet and we will try to help you.

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06-26-2013
07:05 AM

06-26-2013
07:05 AM

As Valery already pointed out the symbilc engine in MC14 and above is muPad, the engine in older versions was Maple, considered by many users as the better one.

muPads behaviour is sometiome annyoing, while mathematically perhaps more correct than that of Maple. Maple obviously is implicitely assuming that X and Y are real values as most of us would do, too, as the "formula" for calculating the absolute value you have in mind is valid for real X and Y only:

So if you want to assume X and Y as real values, you have to tell muPad explicitely so. Additionally you have to demand muPad you want it to simplify the expression.

Maple assumed by default variables and results to be real values and you could change that by using the modifier "complex".

muPad (unfortunately!?) defaults to "complex" and making it think "real" can be quite a challenge sometimes.

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06-26-2013
08:54 AM

06-26-2013
08:54 AM

Re: MathCAD 14 symbolic solver

Thank you all for your quick responses. I feel much better about MC14 now. I also tried the modifier ALL=real which works fine too.

However, with something a bit more complex, I wonder if something else is needed:

MC7:

MC14:

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06-26-2013
10:28 AM

06-26-2013
10:28 AM

Re: MathCAD 14 symbolic solver

As already indicated it can be tricky to convince MC to simplify expressions the way we expect it to do. Sometimes muPad is simply unable to do (its not the best symbolic processor one can imagine), sometimes we are making implicit assumptions we often are not aware of.

Most of the time we end up in trial and error, playing around with the keywords and modifiers. And ever so often MC would ignore a given conditions - thats especially true with the "assume" command.

I didn't typed in the expression but what you can try is "assume, ALL>0", "simplify,max" and somtimes "factor" helps even if we are not interested in a factorization. There are situations where even the order the keywords are typed is important.

After all its an unsatisfyable situation that the possibilities to influence the way symbolic evalauations are done are so much limited.

As Valery already wrote - to make it easier for us you its better to attach a worksheet. You can do so by clicking in the upper right "Use advanced editor".

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06-28-2013
11:24 AM

06-28-2013
11:24 AM

Re: MathCAD 14 symbolic solver

Here are some attempts. Only success with a self defined absolute function

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06-28-2013
02:01 PM

06-28-2013
02:01 PM

Re: MathCAD 14 symbolic solver

Thanks again Werner,

I've set this aside for now. After playing around with both solvers, I've made my peace with the MC14 solver, although, as you pointed out, it does appear to need some coercion, depending on what one is doing. I too was playing with the self-defined absolute function, working with complex matrices, and I got satisfactory results.

Regards,

Raymond