Proof by contraposition

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Proof by Contraposition is an indirect mathematical proof for a conditional sentence P=>Q that relies upon the tautology (P=>Q)<=>(~Q=>~P).

Proof by Contraposition of a Conditional Sentence P=>Q

  1. Assume ~Q.
  2. ...
  3. Therefore, ~P.
  4. Thus, ~Q=>~P
  5. Therefore, P=>Q
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