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QUTADAh1-Visitor
1-Visitor
June 3, 2019
Solved

whats the difference

Hi guys as you see I am using this matrix and want to find eigenvalues and vector but dont understand the difference between two numeric and symbolic solutions, why are they different?

 

Thanks

LucMeekesAnswer
23-Emerald IV
June 3, 2019

You should realize that Mathcad contains a numeric processor an a symbolic processor. They approach your mathematical problem form a different standpoint, and therefore can produce different answers to the same problem.

 

Success!
Luc

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6 replies

Werner_E
Werner_E25-Diamond I
25-Diamond I
June 3, 2019

On contrary to Eigenvalues, Eigenvectors are not unique. Every multiple of an Eigenvector is an Eigenvector, too.

So you are free to use (1;1) as eigenvector or (0.75; 0.75).

Mathcads numerics uses eigenvectors with length 1 while the symbolics doesn't normalizes that way.

 

For future questions: Instead or additionally to pics please always attach your worksheet.

 

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    QUTADAh1-VisitorAuthor
    1-Visitor
    June 3, 2019

    Worksheet is usually long thats why i attach a pic instead..

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    LucMeekes23-Emerald IVAnswer
    23-Emerald IV
    June 3, 2019

    You should realize that Mathcad contains a numeric processor an a symbolic processor. They approach your mathematical problem form a different standpoint, and therefore can produce different answers to the same problem.

     

    Success!
    Luc

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    QUTADAh1-VisitorAuthor
    1-Visitor
    June 3, 2019

    and how do I know which answer I want? thanks!

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    Werner_E
    Werner_E25-Diamond I
    25-Diamond I
    June 3, 2019
    @QUTADAh wrote:

    and how do I know which answer I want? thanks!

    How should we know which answer you need?

    If you don't know why you calculate eigenvectors of a matrix and what you should do with them, you probably don't need to calculate them at all 😉

     

    The worksheet with the eigenvectors sure is not too large and if a worksheet you experience a problem with is too large or contains confident data, you should try to narrow down the problem and create a smaller example sheet which shows the problem/error, too. After all, its hard to debug just a picture and we often need a live worksheet to play with, to find the reason for an error or a suitable workaround.

     

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