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Step * 1 of Lemma classical-double-negation


1. P : ℙ@i'
⊢ {¬¬P ⇐⇒ P}
BY
{ (InstLemma `classical-excluded-middle` [⌜P⌝]⋅ THENA Auto) }

1
1. P : ℙ@i'
2. {P ∨ (¬P)}
⊢ {¬¬P ⇐⇒ P}

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Latex:

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Latex:

1.  P  :  \mBbbP{}@i'
\mvdash{}  \{\mneg{}\mneg{}P  \mLeftarrow{}{}\mRightarrow{}  P\}


By

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Latex:
(InstLemma  `classical-excluded-middle`  [\mkleeneopen{}P\mkleeneclose{}]\mcdot{}  THENA  Auto)

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