Proof of Eigenvalue of A^2 When λ is Eigenvalue of A

In summary, the proof of eigenvalue of A^2 when λ is an eigenvalue of A involves using the definition of eigenvalues and eigenvectors, as well as properties of matrix multiplication and eigenvalues. It is important because it provides a deeper understanding of the relationship between eigenvalues of a matrix and its powers, and can be applied to all matrices with eigenvalues and eigenvectors. The proof also relates to the concept of diagonalization, as it can be used as a step towards diagonalizing a matrix.
  • #1
sana2476
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Homework Statement


Let λ be an eigenvalue of A. Then λ^2 is an eigenvalue of A^2




The Attempt at a Solution



I know I have to start by using the fact that λ is an e.v of A then set up an equation relating the eigenvalues and vectors to A which is: Ax=λx. And I understand that the equation for λ^2 and A^2 would be: A^2(x)=λ^2(x)...but i don't know how to prove that :-(
 
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  • #2
Ax=λx,so AAX=Aλx=λAX=λ*λx,namely A^2(x)=λ^2(x)
 

1. What is the proof of eigenvalue of A^2 when λ is an eigenvalue of A?

The proof involves using the definition of eigenvalues and eigenvectors, as well as properties of matrix multiplication and eigenvalues. It can be shown that if λ is an eigenvalue of A, then λ^2 is an eigenvalue of A^2.

2. Why is it important to prove the eigenvalue of A^2 when λ is an eigenvalue of A?

This proof is important because it provides a deeper understanding of the relationship between eigenvalues of a matrix and its powers. It also allows us to make conclusions about the eigenvalues of A^2 without having to find them individually.

3. Can you explain the intuition behind the proof of eigenvalue of A^2 when λ is an eigenvalue of A?

The proof relies on the fact that an eigenvector of A will also be an eigenvector of A^2. This is because multiplying an eigenvector by A is equivalent to scaling the vector by its corresponding eigenvalue, and this scaling will be repeated when the eigenvector is multiplied by A^2.

4. Is the proof of eigenvalue of A^2 when λ is an eigenvalue of A applicable to all matrices?

Yes, this proof is applicable to all matrices as long as they have eigenvalues and eigenvectors. Matrices with complex eigenvalues and eigenvectors will also follow this proof.

5. How does the proof of eigenvalue of A^2 when λ is an eigenvalue of A relate to the concept of diagonalization?

The proof of eigenvalue of A^2 when λ is an eigenvalue of A is closely related to diagonalization. In fact, this proof can be used as a step towards diagonalizing a matrix, as it shows that the powers of A will have the same eigenvectors as A itself. This is an important concept in understanding diagonalization of matrices.

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