whats the difference

[QUTADAh]

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

[Werner_E]

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.

[QUTADAh]

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

[LucMeekes · Accepted solution]

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

[QUTADAh]

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

[Werner_E]

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@QUTADAh wrote:

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

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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.

[QUTADAh]

Actually I just made this code to ask the question with Symbolic and numeric solutions, I am not directly interested in the eigenvector itself, but this cleared it up now! For the future worksheets I will just narrow down the problem and post the worksheet to make it easier for you guys to play around with.

Thanks alot !