Question 1187790
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1. (A v B) --> C         Premise
2. (~A v D) --> E        Premise
// show C v E

// I am using a conditional proof, lines prefixed with :: are part
// of the conditional proof.

3.:: A                   Conditional Proof (CP) assumption #1
4.:: (A v B)             3, ADDition
5.:: C                   4,1 Modus Ponens (MP)
6.:: ~A                  CP assumption #2
7.:: (~A v D)            6, ADD
8.:: E                   7,2 MP
9.:: C v E               3-8, Proof by Cases (PBC)
10. C v E                3-9, CP

// Explanation:
//  Lines 3-5 show that assuming A true results in C true
//  Lines 6-8 show that assuming A false results in E true
//  Line 9 says "A or ~A" results in "C or E" true. Note
//    that A or ~A must be true.