Sorry it’s only a detail once again but in the Eigenvectors, eigenvalues and orthogonality tutorial you write that
“IN order to determine if a matrix is positive definite, you need to know what its eigenvectors are, and if they are all positive or not.”
This is indeed “eigenvalues” we’re talking about here.
(even more anecdotic on the line below you write “eignevalues” instead of “eigenvalues”)