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Mirrors > Home > ILE Home > Th. List > tbt | GIF version |
Description: A wff is equivalent to its equivalence with truth. (Contributed by NM, 18-Aug-1993.) (Proof shortened by Andrew Salmon, 13-May-2011.) |
Ref | Expression |
---|---|
tbt.1 | ⊢ φ |
Ref | Expression |
---|---|
tbt | ⊢ (ψ ↔ (ψ ↔ φ)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | tbt.1 | . 2 ⊢ φ | |
2 | ibibr 235 | . . 3 ⊢ ((φ → ψ) ↔ (φ → (ψ ↔ φ))) | |
3 | 2 | pm5.74ri 170 | . 2 ⊢ (φ → (ψ ↔ (ψ ↔ φ))) |
4 | 1, 3 | ax-mp 7 | 1 ⊢ (ψ ↔ (ψ ↔ φ)) |
Colors of variables: wff set class |
Syntax hints: ↔ wb 98 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 99 ax-ia2 100 ax-ia3 101 |
This theorem depends on definitions: df-bi 110 |
This theorem is referenced by: tbtru 1252 exists1 1993 reu6 2724 eqv 3234 vprc 3879 bj-vprc 9351 |
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