Here's Terence Tao's blog post about the identity: https://terrytao.wordpress.com/2019/08/13/eigenvectors-from-eigenvalues https://terrytao.wordpress.com/2019/0

Here's Terence Tao's blog post about the identity: https://terrytao.wordpress.com/2019/08/13/eigenvectors-from-eigenvalues https://terrytao.wordpress.com/2019/08/13/eigenvectors-from-...