#mean of diagonal

[peeterjoot]

Eigenvalues of 2x2 matrix: another identity seen on twitter.

[Click here for a PDF version of this post] Here’s another interesting looking twitter math post, this time about 2×2 matrix eigenvalues: Theorem 1.1: Eigenvalues of a 2×2 matrix. Let \( m \) be the mean of the diagonal elements, and \( p \) be the determinant. The eigenvalues of the matrix are given by \begin{equation*} m \pm \sqrt{ m^2 – p }. \end{equation*} This is also not hard to…