Ivan Shishkin, Forest Landscape with Herons

Eigenvalues of a weird matrix

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What are the eigenvalues of the following matrix, defined for n3n\geq 3:
An=(cos(log(n))cos(log(n2))cos(log(nn))sin(log(n))sin(log(n2))sin(log(nn)))A_n=\left(\begin{array}{llll} \cos (\log (n)) & \cos \left(\log \left(n^2\right)\right) & \cdots & \cos \left(\log \left(n^n\right)\right) \\ \sin (\log (n)) & \sin \left(\log \left(n^2\right)\right) & \cdots & \sin \left(\log \left(n^n\right)\right) \end{array}\right)

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Solution by Ancient Tree

0 useful votes

This is a trick question. The matrix is not square, so the notion of eigenvalue is ill-defined.