Why Do Eigenvalues of A+B Equal the Sum of Eigenvalues of A and B?

In summary, The sum of the eigenvalues of A+B is equal to the sum of all the individual eigenvalues of A and B, and this also applies to products. This is because when combining A and B, the eigenvalues are also combined, resulting in the same sum as the individual eigenvalues. This applies to products as well.
  • #1
tatianaiistb
47
0

Homework Statement


I solved a problem that asked me to show that the sum of the eigenvalues of A+B equals the sum of all the individual eigenvalues of A and B, and similarly for products. I just would like to know why is this so...


Homework Equations





The Attempt at a Solution



Is it because we're combining A and B?
 
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  • #2
I forgot to mention A and B are 2 by 2 matrices
 
  • #3
tatianaiistb said:

Homework Statement


I solved a problem that asked me to show that the sum of the eigenvalues of A+B equals the sum of all the individual eigenvalues of A and B, and similarly for products. I just would like to know why is this so...
Since you solved this problem, then you should know why this is so.
tatianaiistb said:

Homework Equations





The Attempt at a Solution



Is it because we're combining A and B?
 

Related to Why Do Eigenvalues of A+B Equal the Sum of Eigenvalues of A and B?

1. What are eigenvalues and eigenvectors?

Eigenvalues and eigenvectors are mathematical concepts used to analyze the properties of a square matrix. Eigenvalues represent the scalar values that scale eigenvectors, which are the special set of vectors that remain in the same direction when multiplied by the matrix.

2. How do eigenvalues and eigenvectors relate to each other?

Eigenvalues and eigenvectors are closely related, as eigenvectors are associated with specific eigenvalues. The eigenvectors determine the direction of the transformation, while the eigenvalues determine the magnitude of the transformation.

3. What are the applications of eigenvalues and eigenvectors?

Eigenvalues and eigenvectors have many applications in science and engineering, including image processing, quantum mechanics, and data analysis. They are also used in machine learning algorithms and in solving differential equations.

4. How are eigenvalues and eigenvectors calculated?

The process of finding eigenvalues and eigenvectors involves solving a characteristic equation, which is formed by subtracting the identity matrix from the original matrix and then taking the determinant. The resulting values are the eigenvalues, and the corresponding eigenvectors can be found by solving a system of linear equations.

5. What are the properties of eigenvalues?

Some important properties of eigenvalues include: they are always complex numbers, the sum of eigenvalues is equal to the sum of the diagonal elements of the original matrix, and the product of eigenvalues is equal to the determinant of the matrix. Additionally, if the matrix is symmetric, the eigenvalues are always real numbers.

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