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DiEqvNotBiNot
⊢
f
≡¬
¬
f
DiEqvNotBiNot
Proof:
1
⊢
¬
f
≡¬
¬¬
f
def. of
2
⊢
¬¬
f
≡¬
¬
f
1
,
Prop
3
f
≡¬¬
f
Prop
4
⊢
f
≡
¬¬
f
3
,
DiEqvDi
5
⊢
f
≡¬
¬
f
2
,
4
,
EqvChain
qed
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2023-09-12
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