document.write( "Question 1030684: I have to construct a proof in propositional logic.
\n" ); document.write( "1.(Z>C) • A
\n" ); document.write( "2. D v (C>D)
\n" ); document.write( "3. ~ D /~ZvP
\n" ); document.write( "The > represents the horseshoe meaning if then, only if. \n" ); document.write( "
Algebra.Com's Answer #645509 by Edwin McCravy(20055)\"\" \"About 
You can put this solution on YOUR website!
\r\n" );
document.write( " 1.(Z>C) • A\r\n" );
document.write( " 2. D v (C>D)\r\n" );
document.write( " 3. ~ D        /~ZvP\r\n" );
document.write( "\r\n" );
document.write( " 4. D v (~C v D)      2, Material implication    \r\n" );
document.write( "\r\n" );
document.write( " 5. D v (D v ~C)      4, Commutation\r\n" );
document.write( "\r\n" );
document.write( " 6. (D v D) v ~C      5, Association\r\n" );
document.write( "\r\n" );
document.write( " 7. D v ~C            6, Tautology or Idempotent \r\n" );
document.write( "\r\n" );
document.write( " 8. ~C                7, 3, Disjunctive syllogism  \r\n" );
document.write( "\r\n" );
document.write( " 9.  Z > C            1, Simplification\r\n" );
document.write( "\r\n" );
document.write( "10. ~Z                9,8, Modus Tollens\r\n" );
document.write( "\r\n" );
document.write( "11. ~Z v P            10, Addition    \r\n" );
document.write( "\r\n" );
document.write( "Edwin
\n" ); document.write( "
\n" );