A direct solution for pairwise rotations in Kaiser's varimax method

The present note contains a completing-the-squares type approach to the varimax rotation problem. This approach yields a direct proof of global optimality of a solution for optimal rotation in a plane. Because varimax rotation can be interpreted as diagonalization of a set of symmetric matrices, the present solution also applies to the diagonalization problem.The author is obliged to Jos M. F. ten Berge for helpful comments.