Start with this putting TTFF under p and TFTF under q p q ~p ~q ∼p∨q (∼p∨q)→ ∼q ————————————————————————————————— T T T F F T F F Under the ~p put the opposite of p. Since p has TTFF, ~p will have FFTT: p q ~p ~q ∼p∨q (∼p∨q)→ ∼q ———————————————————————————————— T T F T F F F T T F F T Under the ~q put the opposite of q. Since q has TFTF, ~q will have FTFT: p q ~p ~q ∼p∨q (∼p∨q)→ ∼q ———————————————————————————————— T T F F T F F T F T T F F F T T We make ∼p∨q out of the columns ~p, q according to the rule: If there are F's on both sides of the disjunction symbol ∨ the disjunction is F, otherwise it's T Since ~p is FFTT and q is TFTF, then only the 2nd row has F under both ~q and p, so it gets F and the other three get T, so under ∼p∨q we put TFTT p q ~p ~q ∼p∨q (∼p∨q)→ ∼q ———————————————————————————————— T T F F T T F F T F F T T F T F F T T T We make (∼p∨q)→∼q out of the columns ∼p∨q and ∼q according to the rule: If there is a T on the left of the conditional symbol → and a T on the right side of the conditional symbol, the conditional is F, otherwise it's T. Since ∼p∨q is TFTT and ~q is FTFT, then the 1st and 3rd rows has F have this, so it gets F in rows 1 and 3 other two get T, so under (∼p∨q)→ ∼q we put FTFT p q ~p ~q ∼p∨q (∼p∨q)→ ∼q ———————————————————————————————— T T F F T F T F F T F T F T T F T F F F T T T T Edwin