Problem: (P > Q) |- (P > (A > Q)) 1 |_ (P > Q) Premise 2 | |_ P Assumption 3 | | |_ A Assumption 4 | | | Q >E 1,2 5 | | (A > Q) >I 3-4 6 | (P > (A > Q)) >I 2-5 Problem: |- ~(P & ~P) 1 | |_ (P & ~P) Assumption 2 | | P &E 1 3 | | ~P &E 1 4 | | # ~E 2,3 5 | ~(P & ~P) ~I 1-4 Problem: (A v B) |- ~(~A & ~B) 1 |_ (A v B) Premise 2 | |_ (~A & ~B) Assumption 3 | | |_ A Assumption 4 | | | ~A &E 2 5 | | | # ~E 3,4 6 | | |_ B Assumption 7 | | | ~B &E 2 8 | | | # ~E 6,7 9 | | # vE 1,3-5,6-8 10 | ~(~A & ~B) ~I 2-9 Problem: (A v ExFx) |- Ex(A v Fx) 1 |_ (A v ExFx) Premise 2 | |_ A Assumption 3 | | (A v Fa) vI 2 4 | | Ex(A v Fx) EI 3 5 | |_ ExFx Assumption 6 | | |_ Fa Assumption 7 | | | (A v Fa) vI 6 8 | | | Ex(A v Fx) EI 7 9 | | Ex(A v Fx) EE 5,6-8 10 | Ex(A v Fx) vE 1,2-4,5-9 Problem: |- AxAy((Fx & ~Fy) > ~x=y) 1 | |_ a Flag 2 | | |_ b Flag 3 | | | |_ (Fa & ~Fb) Assumption 4 | | | | |_ a=b Assumption 5 | | | | | Fa &E 3 6 | | | | | ~Fb &E 3 7 | | | | | Fb =E 4,5 8 | | | | | # ~E 6,7 9 | | | | ~a=b ~I 4-8 10 | | | ((Fa & ~Fb) > ~a=b) >I 3-9 11 | | Ay((Fa & ~Fy) > ~a=y) AI 2-10 12 | AxAy((Fx & ~Fy) > ~x=y) AI 1-11