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KeenS/1-5.v

Created April 7, 2014 16:40
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1-5.v
Theorem DeMorgan3 : forall P Q : Prop, ~(P \/ Q) -> ~P /\ ~Q.
Proof.
intros.
split.
intro.
destruct H.
left.
apply H0.
intro.
destruct H.
right.
apply H0.
Qed.
Theorem NotNot_LEM : forall P : Prop, ~~(P \/ ~P).
Proof.
intros.
intro Q.
apply DeMorgan3 in Q.
destruct Q.
apply H0.
apply H.
Qed.
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