Question 1205405
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1. C ⊃ (D v A) 
2. A ⊃ H
3. ~H           /~C v D

            | 4. ~(~C v D)  Assumption for Indirect Proof
            | 5. ~~C • ~D   4, DeMorgan's law
            | 6. C • ~D     5, Double Negation
            | 7. C          6, Simplification         
            | 8. D v A    1,7, Modus Ponens   
            | 9. ~A       2,3, Modus Tollens
            |10. A v D      8, Commutation
            |11. D       10,9, Disjunctive syllogism
            |12. ~D • C     6, Commutation
            |13. ~D        12, Simplification
            |14. D • ~D 11,13, Conjunction
~C v D     lines 4-14   Indirect Proof

Edwin</pre>