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I
ifomenko1-Visitor
1-Visitor
August 15, 2017
Solved

Bug in symbolic integration?

  • August 15, 2017
  • 2 replies
  • 5045 views

I try to get formula for ellipse area in polar coordinates. I've got it but symbolic result is wrong. I can`t understand why?

Symbolic Area is zero.GIF

One more example with strange behaviour

Symbolic integration bug-2.GIF

 

Best answer by Werner_E

The Mupad version licensed by PTC for Mathcad seems to be very old and also quite limited in functionality (compared to whats possible in Matlab).

2 replies

L
LucMeekes23-Emerald IV
23-Emerald IV
August 16, 2017

No, I'd rather think it's a bug in your formulation of the integral. Why additionally integrate from 0 to 1?

Ellipse.png

I
ifomenko1-VisitorAuthor
1-Visitor
August 16, 2017

Symbolic Area is zero (answer).GIF

L
LucMeekes23-Emerald IV
23-Emerald IV
August 16, 2017

Check my attachment (I've attached the file to my first reply), and see where a difference (if any) occurs.

 

Success!
Luc

W
Werner_E25-Diamond I
25-Diamond I
August 16, 2017

Before evaluting the definite integral, Mathcads symbolics calculates the indefinite one and I guess that the problem lies here.

The expression MuPad calculates seems not to be valid for the full range of t (or its wrong completely?)

I guess that Lucs MC11 with Maple gives a different result

Bild.png

L
LucMeekes23-Emerald IV
23-Emerald IV
August 16, 2017

It is quite different,... and wide.

For the curious I've copied the symbolic result to a new equation, stretched over two lines.

(You don't want to see what symplify does):

EllipseArea.png

 

@WernerExinger wrote:

Before evaluting the definite integral, Mathcads symbolics calculates the indefinite one and I guess that the problem lies here.

Then why is the polar plot already different?

 

Luc

I
ifomenko1-VisitorAuthor
1-Visitor
August 16, 2017

unfortunately,assumptions a>0,b>0,t=real don't change situation.

what about MC Prime 4?

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