That is not true. You should change diagonal by scalar. Try now.
Fernando Revilla
That is not true. You should change diagonal by scalar. Try now.
Fernando Revilla
Can you be more precise about what you are trying to prove?
It is true that the only matrices that commute with all diagonal matrices are themselves diagonal matrices.
But it is not true that the the only sets of commuting matrices are diagonal. For example, the matrices all commute with each other.
I understood the problem in the same way, but the result is false. Choose:
is diagonal and however
In Drexel28's web there is a proof that a matrix conmutes with all matrices iff is an scalar matrix.
Fernando Revilla