1. (AvB) -> C
2. (CvD) -> E
3. CvA
4. ~C
.: E
5. A 3,4,DS (disjunctive syllogism)
6. AvB 5,addition (disjunctive addition)
7. C 1,6,MP (modus ponens)
8. CvD 7,addition (disjunctive addition)
9. E 2,8,MP (modus ponens)
----------------------------
1. X->Y
2. X->Z
.: X->(Y&Z)
3. ~XvY 1,writing a conditional
as a disjunction
4. ~XvZ 2,writing a conditional
as a disjunction
5. (~XvY)&(~XvZ) 3,4,conjunction
6. ~Xv(Y&Z) 5,distributive [" taking out ~Xv "]
7. X->(Y&Z) 6,writing a disjunction as
a conditional
-----------------------------
1. ~(A&(BvC)) .: A->~B
2. ~((A&B)v(A&C)) 1, distributive
3. ~(A&B)&~(A&C) 2, deMorgan's
4. ~(A&B) 3, simplification
5. ~Av~B 4, deMorgan's law
6. A->~B 5,writing disjunction
as a conditional
Edwin