Handout based on section 4.3; includes exercise 12 from that section and 5 proofs of implications and biconditionals taken from that section.

Just do parts a,c,e,g of problem 12.

Due Monday, March 6.

Just to be completely clear, here are the statements to be formally proved on the first page (mod the typos I inevitably introduced on this first pass -- one point to the first student who points out each typo :-): (Ex.~Px) <-> ~(Ax.Px) (Ex.(Px | Qx)) <-> ((Ex.Px) | (Ex.Qx)) (Ax.(Px | S)) <-> (Ax.Ps) | S (where x does not occur free in S!) (Ax.(Px -> Qx)) -> ((Ex.Px) -> (Ex.Qx)) (Ey.(Ax.Rxy)) -> (Ax.(Ey.Rxy))