"orthonormal columns imply orthonormal rows for square matrix."(adsbygoogle = window.adsbygoogle || []).push({});

My proof is:

[itex]Q^{T}Q=I[/itex](orthonormal columns)

implys

[itex]QQ^{T}=I[/itex](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?

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# Unitary matrix question

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