Abelian Groups Have One-Dimensional Irreducibles Representation Theory Irreducibility of $V_n$ Representation Theory Change Of Basis For Bilinear Forms Linear Algebra Single-Variable Presentation of $R_u$ Algebra Sum And Intersection Of Subspaces Linear Algebra $\operatorname{SO}(3) \cong \mathrm{PSU}(2)$ — Proof Sketch Representation Theory Decomposition of a Finite-Type Cartan Matrix into Connected Dynkin Components Algebra Fundamental Theorem of Galois Theory Algebra Algebra Area