How many Venn diagrams can be formed using two sets within a universe S? Are they all exhibited below?
In this applet, A and B are subsets of a universal set S. The list above gives the 16 different subsets of S that can be constructed from A and B using the basic set operations of union ($\cup$), intersection ($\cap$), and complement ($^c$). The selected subset is colored red in the Venn diagram on the right.
(From zombie-page http://michaelshepperd.tripod.com/VennDiagramApplet/VennGame.html - I had to modify it to elimate popups, cookies, and other evils.... ael)