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Student Support Forum: 'Eigenvectors and substitutions' topicStudent Support Forum > General > "Eigenvectors and substitutions"

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Giorgio
04/18/02 2:27pm

I want to calculate the eigenvectors of the square matrix
m={{k1/I1,-k1/I1},{(-I3k1+I1k2)/(I2 I3),(I2k2+I3(k1+k2))/(I2I3)}}

If now I want to evaluate the matrix for the case I1=I2=I3 and k1=k2 and then calculate the eigenvectors, that is Eigenvectors[m/.I{2->I1,I3->I1,k2->k1}]
I obtain the correct result
{{1,0},{0.5,-1}}.

If on the other side I calculate
Eigenvectors[m]/.{I2->I1,I3->I1,k2->k1}
I obtain an error of infinite value. In fact Eigenvectors[m] contains a denominator with the polynomial
-I1^2k1 +Sqrt[I1^4 k1^2]
that goes to zero if simplified.

Does anyone know the reason for this? Is it due to the way Mathematica treates variables?
How can I obtain an expression of the eigenvectors that is not affected by this problem?

Thanks in advance
Giorgio

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Subject (listing for 'Eigenvectors and substitutions')
Author Date Posted
Eigenvectors and substitutions Giorgio 04/18/02 2:27pm
Re: Eigenvectors and substitutions Henry Lamb 04/24/02 03:42am
Re: Eigenvectors and substitutions Giorgio 04/25/02 11:16am
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