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akalim1-Visitor
1-Visitor
October 1, 2015
Question

How to solve this integral..?

  • October 1, 2015
  • 3 replies
  • 3993 views

I have a function w(x,y) :

Untitled1.png

I want to evaluate the followng integral :

Untitled2.png

I have defined then vlaues of constants a & b. I want an expression interms of constants C11, C13, C31, C33, D and variables x and y.

But when i try to evaluate this integral, it gives the following error:

Untitled3.png

How to solve this integral? I have attached the mathcad (Prime 3.1) file. I would be really greatful if someone could help me with this.

3 replies

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LucMeekes23-Emerald IV
23-Emerald IV
October 1, 2015

Let's first establish that there's no error in w(x,y)

{While in no way implying that that would, could or should be the cause of the error you experience.}

the first term is C11 multiplied with the the sine of pi * x divided by a and multiplied with the sine of pi * (again) x, now divided by b.

Ar you sure that the seond x should be an x, not a y?

It seems so inconsistent with the other terms.

Luc

    L
    LucMeekes23-Emerald IV
    23-Emerald IV
    October 1, 2015

    Here are both answers to the integral themselves:

    Notice that the first solution (also) depends on nu, whereas the second only depends on a, b and the C's.as you wanted.

    Assuming my assumption is correct, with

    You can write w as:

    and get:

    Maybe you are leading Prime astray by forcing it to equate the integral to U13....

    Success!
    Luc

      A
      akalim1-VisitorAuthor
      1-Visitor
      October 1, 2015

      Thanks a lot LucMeekes. You are right, the expression for w(x,y) that i had written was indeed wrong. It should actually be y instead of x. A careless error on my part. Thanks for pointing that out.

      I have actually tried to not equate it with U13. I wrote the expression separately and then tried to evaluate, but it still gives the same error. The screen shot you have attached is somehow not visible, so i don't know what else you have changed to make it work. Can you upload a clearer version of the picture.?

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      LucMeekes23-Emerald IV
      23-Emerald IV
      October 1, 2015

      If you click ON the picture it will enlarge.

      A
      akalim1-VisitorAuthor
      1-Visitor
      October 1, 2015

      Its visible now. Previously it was not visible even if clicked. Anyways thanks a lot. I will try the matrix method.

      A
      akalim1-VisitorAuthor
      1-Visitor
      October 1, 2015

      Its not working. I tried the matrix approach, this time it does not give a error message instead keeps on calculating forever. I believe your version is Mathcad 15 and it seems to have no problem with this expression. I dont know why prime 3.1 cannot calculate this.

      L
      LucMeekes23-Emerald IV
      23-Emerald IV
      October 2, 2015

      Nope, mine is mathcad 11, and it has no problems with the integral. If you have the full version of Prime, you can also install (or maybe already have installed) Mathcad 15. You can open my attachment (integral.mcd.zip) with mathcad 15 and calculate it.

      The important difference (wrt this topic) between mathcad 11 <> 15 is the symbolic engine. Mathcad 11 uses 'maple', whereas 15 (no, it started at 14 and goes onto Prime) uses 'mupad'.

      Success!
      Luc.

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