Fixed typo in dual systems.

src/fa/duality/definitions.tex

@@ -9,7 +9,7 @@
         \item For any $y_0 \in E$, if $\lambda(x, y_0) = 0$ for all $x \in E$, then $y_0 = 0$.
     \end{enumerate}
 
-    The mapping $\lamdba: E \times F \to K$ is the \textbf{canonical bilinear form} of the duality, denoted $(x, y) \mapsto \dpn{x, y}{\lambda}$, and the duality $(E, F, \lambda)$ is denoted $\dpn{E, F}{\lambda}$. 
+    The mapping $\lambda: E \times F \to K$ is the \textbf{canonical bilinear form} of the duality, denoted $(x, y) \mapsto \dpn{x, y}{\lambda}$, and the duality $(E, F, \lambda)$ is denoted $\dpn{E, F}{\lambda}$. 
 
     In the context of a dual system, $E$ and $F$ are identified as subspaces of each others' algebraic duals. 
 \end{definition}