Created
January 9, 2014 00:05
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double negated lem
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| Goal forall T, ~~(T + ~T). | |
| Proof. | |
| intros T negLEM. | |
| cut (~T). | |
| - intro negT. | |
| apply (negLEM (inr negT)). | |
| - intro t. | |
| apply (negLEM (inl t)). | |
| Defined |
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