HW #4 (due on March 19th)

(1) Use a truth-table to test the following sequents for validity (i.e., turn in a copy of the truth-table and indicate whether it shows the sequent is valid or invalid):

(a) (P->Q), ~P |- ~Q

(b) ((PVQ)&~(P&Q)), P |- ~Q

(c) P |- (Q->P)

(2) Determine the truth-values of the following wffs under any interpretation making P=T, Q=F, R=T, and S=T

(a) ((PVQ)&~(R&S))

(b) (P->(~RV~S))

(c) (Q->(S&Q))