CSCI 6610		  Automata and Formal Languages		     Spring 2004

			        Homework set #6

		    *** Due in class on Tuesday, April 13 *** 

            These exercises/problems are all from the text by Sipser.

NOTES: "Show" always means PROVE in the exercise/problem descriptions.
       Be sure to consult the note below for any problem followed by a * in the 
       listing, as this indicates a hint and/or directions.
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	8.1* (10 pts.)
	8.5  (20 pts.)
	8.6  (10 pts.)
	8.8* (20 pts.)
	8.9* (10 pts.)
	8.11 (15 pts.)
	8.16 (15 pts.)

************   Directions and/or Hints   ****************

* 8.1:  see Sipser p. 294 for the read-only input T.M. model.

* 8.8:  you may assume that log-space reducibility is transitive.
	We will prove this in class; the general idea is similar
	to the proof of Thm. 8.18.

* 8.9:  you may find it useful to prove that if A is polynomial 
	time reducible to B and B is in NP, then A must be in NP.
	This is similar to Thm. 7.25.