Exercise 5.4.25

Answers

1.
Let Eλ be a eigenspace of T corresponding to the eigenvalue λ. For every v Eλ we have
TU(v) = UT(v) = λU(v).

This means that Eλ is an U-invariant subspace. Applying the previous exercise to each Eλ, we may find a basis βλ for Eλ such that [UEλ]βλ is diagonal. Take β to be the union of each βλ and then both [T]β and [U]β are diagonal simultaneously.

2.
Let A and B are two n × n matrices. If AB = BA, then A and B are simultaneously diagonalizable. To prove this we may apply the version of linear transformation to LA and LB.
User profile picture
2011-06-27 00:00
Comments