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{\large \bf CS-520 \hspace{1.2in} Introduction to Formal Models
\hspace{.5in}
Fall 1997}

\vspace{.1in}

\begin{center}
{\large \bf Homework 1}
\end{center}


This homework is due in class on September 10. Each problem is worth
10 points.

\begin{enumerate}
\item
On a page separate from the remaining problems,
attach a photo of yourself. Write your name next to the photo. 
Underneath the photo, write 1-2 sentences describing why you are
taking this course and what you would like to learn from it.
If you like, please also describe a little about yourself and your
interests.

Your page will be photocopied and returned to you with the
rest of the homework.
\item
Give regular expressions for the languages described in Exercise 1.4
page 84 parts b,f and l. You don't need to include proofs that your
regular expressions are correct. (However it is a good idea to at least
check your expressions on several examples before handing them in.)
\item
Let $R$ be a regular expression that describes the language of strings
with an even number of 0's and an even number of 1's. For example,
$R$ could be:
\[
	(00 \cup 11 \cup (01 \cup 10)(00 \cup 11)^* (01 \cup 10))^*
\]
Explain why the following regular expression describes the language
of strings with an even number of 0's and an odd number of 1's:
\[
	R (1 \cup 01(11)^*0)R
\]
\end{enumerate}
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