Fix typo in "dicsrete"

chapters/equations.tex

@@ -640,7 +640,7 @@ \section{Events and Synchronization}\label{events-and-synchronization}
 above1 = noEvent(x1 > 1);            // above1 is discrete-time variable
 \end{lstlisting}
 The when-condition error is a direct violation of the requirement that the when-condition must be discrete-time.
-The error in the equation with \lstinline!above1! is only indirect; since \lstinline!above1! requires a dicsrete-time solution, it cannot be solved from this equation.
+The error in the equation with \lstinline!above1! is only indirect; since \lstinline!above1! requires a discrete-time solution, it cannot be solved from this equation.
 Consequently, this equation cannot be solved for any variable, a structural singularity condition that will be reported in tool-specific ways.
 \end{example}