Artin-Wedderburn
Statement
Let $A$ be a central simple algebra over $F$. Then $$A\cong M_n(D),$$ where $D$ is a division $F$-algebra that is unique up to isomorphism.
Let $A$ be a central simple algebra over $F$. Then $$A\cong M_n(D),$$ where $D$ is a division $F$-algebra that is unique up to isomorphism.