Mathbox for Richard Penner |
< Previous
Next >
Nearby theorems |
||
Mirrors > Home > MPE Home > Th. List > Mathboxes > frege55a | Structured version Visualization version GIF version |
Description: Proposition 55 of [Frege1879] p. 50. (Contributed by RP, 24-Dec-2019.) (Proof modification is discouraged.) |
Ref | Expression |
---|---|
frege55a | ⊢ ((𝜑 ↔ 𝜓) → if-(𝜓, 𝜑, ¬ 𝜑)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | frege54cor1a 40230 | . 2 ⊢ if-(𝜑, 𝜑, ¬ 𝜑) | |
2 | frege53a 40226 | . 2 ⊢ (if-(𝜑, 𝜑, ¬ 𝜑) → ((𝜑 ↔ 𝜓) → if-(𝜓, 𝜑, ¬ 𝜑))) | |
3 | 1, 2 | ax-mp 5 | 1 ⊢ ((𝜑 ↔ 𝜓) → if-(𝜓, 𝜑, ¬ 𝜑)) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 → wi 4 ↔ wb 208 if-wif 1057 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-frege8 40175 ax-frege28 40196 ax-frege52a 40223 ax-frege54a 40228 |
This theorem depends on definitions: df-bi 209 df-an 399 df-or 844 df-ifp 1058 |
This theorem is referenced by: frege55cor1a 40235 |
Copyright terms: Public domain | W3C validator |