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Multiple integration Problme

akalim
1-Newbie

Multiple integration Problme

I want to integrate the following expression in mathcad.

Untitled.png

the answer should be the following if p(r)=po=constant

Untitle11d.png

But when i try to solve this expression in mathcad i get this:

Untitleffd.png

It should give 64 instead of 24. What am i doing wrong.?

4 REPLIES 4
AlanStevens
15-Moonstone
(To:akalim)

Try:

integrals.PNG

Alan

Werner_E
24-Ruby V
(To:akalim)

It should give 64 instead of 24. What am i doing wrong.?

Hard to tell without seeing the sheet. And if you attach your sheet, chances are, I am not able to open it, if its not Prime 3.0 or below. Thats the PTC way of usability and compatibility:-(

In the way you typed in your expression, the integrand r*(1/r)*(1/r) simplifies to 1. So the first integral gives you r, the second r^2/2, the third r^3/6 and finally the last one r^4/24. So Mathcad/Prime is correct with its answer.

If you type in the integral(s) you really want to evaluate, you will get the result you expect.

Here is what Mathcad 15 comes up with

When I type in the expression, beginning with the inner integral, the parenthesis are set automatically by Mathcad, but can be deleted manually without any problem, as you can see in the second expression. If you start with the outer integral, the parenthesis are not set at all. That behavior can be different in Prime (I am too lazy to try and wait for  Prime to start up).

LucMeekes
23-Emerald II
(To:akalim)

The explanation for your last result is found as follows:

But that isn't what you set out with.

Some food for thought (Mathcad 11):

Success!

Luc

akalim
1-Newbie
(To:akalim)

Thanks a lot guys. Its working now.

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