# unitary matrix question

by td21
Tags: matrix, unitary
 P: 74 "orthonormal columns imply orthonormal rows for square matrix." My proof is: $Q^{T}Q=I$(orthonormal columns) implys $QQ^{T}=I$(orthonoraml rows) for square matrix. But i think this proof is kind of indirect. Is there another more direct proof from the definition of inner product or norm?
 Emeritus Sci Advisor PF Gold P: 8,992 I think that's as direct and simple as it gets. I would only add the explanation of how $Q^TQ=I$ implies $QQ^T=I$.

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