Solving Diagonal Matrix Homework: AB=BA

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SUMMARY

The discussion centers on proving that two diagonalizable matrices A and B, which share the same eigenvectors, commute, i.e., AB = BA. The key insight is that both matrices can be represented in a diagonal form using a common matrix P, such that P-1AP and P-1BP are diagonal matrices. Since diagonal matrices commute, the conclusion follows that AB = BA holds true under these conditions.

PREREQUISITES
  • Understanding of diagonalizable matrices
  • Familiarity with eigenvectors and eigenvalues
  • Knowledge of matrix representation and transformation
  • Basic linear algebra concepts
NEXT STEPS
  • Study the properties of diagonal matrices and their commutativity
  • Learn about eigenvalue decomposition and its applications
  • Explore the implications of shared eigenvectors in linear transformations
  • Investigate the role of similarity transformations in linear algebra
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Students of linear algebra, mathematicians, and anyone involved in theoretical aspects of matrix operations and properties.

arshavin
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Homework Statement



Suppose the matrix A , B are diagonalizable and have the same eigenvectors. Show AB=BA


Homework Equations





The Attempt at a Solution



There exists a matrix P s.t. (P^-1)AP=(P^-1)BP

I played around with this, and could not get anywhere..
 
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If A is diagonalizable then there is a basis where it's a diagonal matrix. Then all of the basis vectors are eigenvectors. If B has the same eigenvectors then it's also a diagonal matrix in the same basis. Now you just have to show two diagonal matrices commute.
 

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