Subject: HW 8
From: "William J. Rapaport" <rapaport@buffalo.edu>
Date: Fri, 6 Nov 2009 07:32:24 -0500 (EST)

A student emailed me this morning with the following question:
"I was wondering if you could explain the union and intersection of a
collection of sets. I can't quite grasp it too well.  I'll be a little
more specific. You give us a hint, saying to compute A1, A2, etc. What
is A1 in context to the problem?"

My reply:  UiAi = A1 u A2 u ...

You're given a formula defining Ai for each i.

So, to figure out what UiAi is, figure out what the first few Ai's look
like: A1, A2, etc.

Then take their union: union the first two, then union that with the
third, etc.

Look at problems 45 and 49 and examples 16 and 17.