Symmetric Matrices
http://www.maa.org/taxonomy/term/42335/0
enFields for Which the Principal Axis Theorem Is Valid
http://www.maa.org/programs/faculty-and-departments/classroom-capsules-and-notes/fields-for-which-the-principal-axis-theorem-is-valid
<div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><em>One version of the Principal Axis Theorem asserts that any symmetric matrix with entries in \( \mathcal{R}\) is similar over \(\mathcal{R}\) to a diagonal matrix. The authors find necessary and sufficient conditions for a field \(K\) that make the Principal Axis Theorem valid over \(K\).</em></p>
</div></div></div>Classroom Capsules and Notes for Symmetric Matrices in Linear Algebra
http://www.maa.org/programs/faculty-and-departments/course-communities/classroom-capsules-and-notes-for-symmetric-matrices-in-linear-algebra