BoxEqvTrueYields

⊢ f ≡true f BoxEqvTrueYields

Proof:

1
⊢ true ; ¬f ≡¬f
2
⊢ ¬(true ; ¬f) ≡¬¬f
1,Prop
3
⊢ f ≡¬¬f
4
⊢ f ≡¬(true ; ¬f)
2, 3,Prop
5
⊢ f ≡true f
4, def. of 

qed

2024-08-03
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