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Mirrors > Home > MPE Home > Th. List > Mathboxes > frege55aid | Structured version Visualization version GIF version |
Description: Lemma for frege57aid 41440. Core proof of Proposition 55 of [Frege1879] p. 50. (Contributed by RP, 24-Dec-2019.) |
Ref | Expression |
---|---|
frege55aid | ⊢ ((𝜑 ↔ 𝜓) → (𝜓 ↔ 𝜑)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | bicom1 220 | 1 ⊢ ((𝜑 ↔ 𝜓) → (𝜓 ↔ 𝜑)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 205 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 |
This theorem depends on definitions: df-bi 206 |
This theorem is referenced by: frege56aid 41438 |
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