[Math] Orthogonal columns imply orthogonal rows

linear algebramatricesorthogonality

The original question is: Column Vectors orthogonal implies Row Vectors also orthogonal?

A counterexample with zero entries is given in one post. However, my question is whether pairwise orthogonal columns with no zero entries imply pairwise orthogonal rows?

Best Answer

The answer is no. Here's a counterexample: $$ \pmatrix{1&2\\-1&2} $$

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