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which are diagonalizable over $\mathbb{C}$
Which of the following matrices are diagonalizable over $\mathbb{C}$.
(a) Any $n×n$ unitary matrix with complex entries.
(b) Any $n×n$ hermitian matrix with complex entries.
(c) Any $n×n$ strictly upper triangular matrix with complex entries.
(d) Any $n×n$ matrix with complex entries whose eigenvalues are real.
how to solve this problem.can you help me please?thanks for your help.