For a paper summarizing the most important theorems and proofs of regression theory.

1. Click here for the Theorems, containing the following:

• 1. The eigenvalues of a symmetric matrix are real
• 2. The eigenvectors of a symmetric matrix corresponding to distinct eigenvalues are orthogonal
• 3. If λ_i is a repeated root with multiplicity m>=2, then there exist m orthonormal vectors corresponding to λ_i