Difference between revisions of "Eigenvalue"

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{{merge|eigenvector}}
 
{{merge|eigenvector}}
An '''eigenvalue''' of a square [[matrix]] <math>A</math> is a [[real|real number]] or [[complex number]] <math>\lambda</math> such that
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An '''eigenvalue''' of a square [[matrix]] <math>A</math> is a [[complex number]] <math>\lambda</math> such that
  
 
:<math>A\boldsymbol{x}=\lambda\boldsymbol{x}</math>
 
:<math>A\boldsymbol{x}=\lambda\boldsymbol{x}</math>
  
for some non-zero vector <math>\boldsymbol{x}\in\mathbb{R}</math> known as a [[eigenvector]]. The eigenvalues are the zeroes of a matrix's [[characteristic polynomial]].
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for some non-zero vector <math>\boldsymbol{x}\in\mathbb{R}</math> known as a [[eigenvector]]. The eigenvalue is the zero of a matrix's [[charateristic polynomial]].
 
 
The product of all the eigenvalues of a matrix equals the value of the matrix's determinant.  Since a matrix is invertible if and only if the determinant is non-zero, it is invertible if and only if zero is not an eigenvalue.
 
  
 
The [[span]] of all the eigenvectors corresponding to a fixed eigenvalue <math>\lambda</math> is called the [[eigenspace]] <math>E_\lambda</math> of <math>A</math>.
 
The [[span]] of all the eigenvectors corresponding to a fixed eigenvalue <math>\lambda</math> is called the [[eigenspace]] <math>E_\lambda</math> of <math>A</math>.
  
 
[[category:Linear algebra]]
 
[[category:Linear algebra]]

Revision as of 16:46, May 2, 2010

It has been suggested that this article or section be merged with [[::eigenvector|eigenvector]]. (Discuss)

An eigenvalue of a square matrix <math>A</math> is a complex number <math>\lambda</math> such that

<math>A\boldsymbol{x}=\lambda\boldsymbol{x}</math>

for some non-zero vector <math>\boldsymbol{x}\in\mathbb{R}</math> known as a eigenvector. The eigenvalue is the zero of a matrix's charateristic polynomial.

The span of all the eigenvectors corresponding to a fixed eigenvalue <math>\lambda</math> is called the eigenspace <math>E_\lambda</math> of <math>A</math>.