document.write( "Question 869909: Given
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Algebra.Com's Answer #524593 by jim_thompson5910(35256)\"\" \"About 
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document.write( "Given \r\n" );
document.write( "1.  P ≡ ~C\r\n" );
document.write( "2.  ~(P & D)\r\n" );
document.write( "3.  D\r\n" );
document.write( "Prove C\r\n" );
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document.write( "4.  ~P v ~D                             2         De Morgan's Law\r\n" );
document.write( "5.  ~D v ~P                             4         Commutation\r\n" );
document.write( "6.  ~~D                                 3         Double Negation\r\n" );
document.write( "7.  ~P                                  5,6       Disjunctive Syllogism\r\n" );
document.write( "8.  (P -> ~C) * (~C -> P)               1         Material Equivalence\r\n" );
document.write( "9.  (~C -> P) * (P -> ~C)               8         Commutation\r\n" );
document.write( "10. ~C -> P                             9         Simplification\r\n" );
document.write( "11. ~C -> ~~P                           10        Double Negation\r\n" );
document.write( "12. ~~C                                 11,7      Modus Tollens\r\n" );
document.write( "13. C                                   12        Double Negation\r\n" );
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