Fix minor math formatting

chapters/functions.tex

@@ -1311,13 +1311,10 @@ \subsection{Using the Derivative Annotation}\label{using-the-derivative-annotati
 If the Modelica function call is a $n$th derivative ($n \geq 1$), i.e.\ this function call has been derived from an $(n-1)$th derivative by differentiation inside the tool, an \lstinline!annotation(derivative(order=$n+1$) = $\ldots$)!, specifies the $(n+1)$th derivative, and the $(n+1)$th derivative call is constructed as follows:
 \begin{itemize}
 \item
-  The input arguments are appended with the (n+1)th derivative, which
-  are constructed in order from the $n$th \lstinline!order! derivatives.
+  The input arguments are appended with the $(n+1)$th derivative, which are constructed in order from the $n$th \lstinline!order! derivatives.
 \item
-  The output arguments are similar to the output argument for the $n$th
-  derivative, but each output is one higher in derivative order. The
-  outputs must have the same type and declaration order for the function
-  and its derivative.
+  The output arguments are similar to the output argument for the $n$th derivative, but each output is one higher in derivative order.
+  The outputs must have the same type and declaration order for the function and its derivative.
 \end{itemize}
 
 \begin{nonnormative}