--- a/hw04.tex	Fri Oct 12 05:45:48 2012 +0100
+++ b/hw04.tex	Sun Oct 14 23:41:49 2012 +0100
@@ -11,6 +11,9 @@
 \section*{Homework 4}
 
 \begin{enumerate}
+\item Why is every finite set of strings a regular language?
+
+
 \item Give an automaton that can recognise the language 
 $L(a^*\cdot b\cdot b^*\cdot(a\cdot a^*\cdot b\cdot b^*)^*)$.
 
@@ -18,13 +21,25 @@
 string $s$. Given the following \emph{reversing} function on regular 
 expressions
 
+\begin{center}
+\begin{tabular}{r@{\hspace{1mm}}c@{\hspace{1mm}}l}
+$rev(\varnothing)$   & $\dn$ & $\varnothing$\\
+$rev(\epsilon)$         & $\dn$ & $\epsilon$\\
+$rev(c)$                      & $\dn$ & $c$\\
+$rev(r_1 + r_2)$        & $\dn$ & $rev(r_1) + rev(r_2)$\\
+$rev(r_1 \cdot r_2)$  & $\dn$ & $rev(r_2) \cdot rev(r_1)$\\
+$rev(r^*)$                   & $\dn$ & $rev(r)^*$\\
+\end{tabular}
+\end{center}
+
+
 and the set
 
 \begin{center}
 $Rev\,A \dn \{s^{-1} \;|\; s \in A\}$
 \end{center}
 
-prove that
+prove whether
 
 \begin{center}
 $L(rev(r)) = Rev (L(r))$