1. A --> B       Premise

2. A V C         Premise

3. B --> D       Premise

// prove this leads to ~C --> E V D



4. :: ~C             Conditional Proof (CP) assumption #1

5. :: A              4,2  Disjunctive Syllogism (DS)

6. :: B              5,1  Modus Ponens (MP)

7. :: D              6,3  MP

8. :: ~C --> D       4-7  CP

9. :: ~C --> D v E   8  Addition (ADD)

10.:: ~C --> E v D   9  Commutative Property

11. ~C --> E v D     4-10 CP, discharges CP assumptions





 

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