Suppose U is a finite-dimensional vector space and T∈L(U).
(a) Suppose F=R. Prove that T is diagonalizable if and only if there is a basis of U such that the matrix of T with respect to this basis equals its transpose.
(b) Suppose F=C. Prove that T is diagonalizable if and only if there is a basis of U such that the matrix of T with respect to this basis commutes with its conjugate transpose.
This exercise adds another equivalence to the list of conditions equivalent to diagonalizability in 5.55.