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M
mshaw-31-Visitor
1-Visitor
October 9, 2014
Solved

Definite Integral Issue with Mathcad 15

  • October 9, 2014
  • 15 replies
  • 6743 views

Hi there,

Not sure if I have an incorrect implementation/setup or if it's some kind of bug...

If I perform the following in Mathcad 2001i, it works instantly:

Mathcad+2001i.PNG

If I perform the same in Mathcad 15 it will not solve and I eventually I get the message "Condition contains Otherwise in subexpression".

Mathcad+15.PNG

I have attached the files I have been using for your perusal.

Best answer by Werner_E

I agree with Richard and others that integrals and especially definite integrals alway were a nightmare when the symbolics changed to MuPad. I still remember the many clearly wrong results of rather simple definite Integrals in Mathcad 14 and the some even in the first release of MC15.

This one here is really bad, especially given that its an easy one and consequently the indefinite interal is no problem, not even for Mupad.

That way we can create a workaround here:

1.png

The problem may arise because Mupad defaults to domain complex and that way probably has to make more distinction of cases as we may think of. Not sure about that, though.

If I tell Mathcad/MuPad that all variables are real and positive, I get a result but its frightening and takes quite long to calculate! I am not even sure its correct and equivalent to the above. Not sure whats going on here.

2.png.......

15 replies

M
MikeArmstrong1-Visitor
1-Visitor
October 9, 2014

I also get an error message, looks like a bug to me.

M
mshaw-31-VisitorAuthor
1-Visitor
October 9, 2014

Thanks.

Wasn't sure if I had any settings at error within the worksheet. I don't think I do, I literally loaded Mathcad and entered the equation.

If it is a bug - do the PTC devs look in on these forums? Or would I need to submit to somewhere first?

Thankyou.

M
MikeArmstrong1-Visitor
1-Visitor
October 9, 2014

Mike Shaw wrote:

Thanks.

If it is a bug - do the PTC devs look in on these forums? Or would I need to submit to somewhere first?

Thankyou.

I think you will have to raise a Customer Support call to the Technical Support department. See http://www.ptc.com/cs/doc/copen.htm for how to contact PTC technical support.

V
ValeryOchkov24-Ruby IV
24-Ruby IV
October 9, 2014

Mathcad 2001i has a Maple symbolic engine

Mathcad 13-15 - MuPad symbolic engine

But Maple is Maple - the best symbolic tool!

M
mshaw-31-VisitorAuthor
1-Visitor
October 9, 2014

Interesting, I didn't know that - thankyou.

R
RichardJ19-Tanzanite
19-Tanzanite
October 9, 2014

The MuPad symbolic engine has always been very weak when it comes to integrals, and especially definite integrals. In this case it can solve the indefinite integral, but not the definite integral, which is not logical. This is not the first example I've seen where this is the case though.

At a minimum, the error message is clearly a bug.

    S
    StuartBruff23-Emerald V
    23-Emerald V
    October 9, 2014

    Richard Jackson wrote:

    The MuPad symbolic engine has always been very weak when it comes to integrals, and especially definite integrals. In this case it can solve the indefinite integral, but not the definite integral, which is not logical. This is not the first example I've seen where this is the case though.

    Interesting. That's definitely something to bear in mind.

    At a minimum, the error message is clearly a bug.

    Maybe, Maybe Not. At a Mathcad level, probably, but it's possibly telling us something the internal error that MuPad encountered.

    Stuart

    Werner_E
    Werner_E25-Diamond IAnswer
    25-Diamond I
    October 9, 2014

    I agree with Richard and others that integrals and especially definite integrals alway were a nightmare when the symbolics changed to MuPad. I still remember the many clearly wrong results of rather simple definite Integrals in Mathcad 14 and the some even in the first release of MC15.

    This one here is really bad, especially given that its an easy one and consequently the indefinite interal is no problem, not even for Mupad.

    That way we can create a workaround here:

    1.png

    The problem may arise because Mupad defaults to domain complex and that way probably has to make more distinction of cases as we may think of. Not sure about that, though.

    If I tell Mathcad/MuPad that all variables are real and positive, I get a result but its frightening and takes quite long to calculate! I am not even sure its correct and equivalent to the above. Not sure whats going on here.

    2.png.......

    V
    VladimirN24-Ruby IV
    24-Ruby IV
    October 10, 2014

    I have the following result (as in MC2001i) by using "simplify" and "assume" symbolical operators in the MC15 F000 service release:

    Pic_1.png

    Pic_2.png

    Pic_3.png

    R
    RichardJ19-Tanzanite
    19-Tanzanite
    October 10, 2014

    In MC15 030 I get something different:

    intetgral.png

    If I add z to the list I get the desired result:

    Integral2.png

    If I also add L to the list I get a big, ugly answer that's similar to, but not the same as, the one Werner shows.

    So the trick seems to be to force the domain of all the variables in the kernal, but not the limits.

    R
    RichardJ19-Tanzanite
    19-Tanzanite
    October 10, 2014

    Major symbolic weirdness! I just did it again. If I have only Z and X in the list I get the incomplete solution. Then I copy and paste the expression and add z to the list, and I get the desired solution. BUT, if I then disable calculation for the first expression and enable it again, it also gives the desired solution!

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