Dual Map Is Linear Linear Algebra Degree of a One-Step Construction Algebra Dimension Formula For Subspace Sums Linear Algebra Determinant Invertibility Criterion Linear Algebra Non-Vanishing Trace for Separable Extensions Galois Theory Localization of an $S^{-1}R$-module Algebra Classification of Semisimple Lie Algebras by Cartan Matrix Algebra SO3 Rotation Theorem Group Theory Algebra Area Linear Algebra Subarea