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Mirrors > Home > ILE Home > Th. List > bicom | GIF version |
Description: Commutative law for equivalence. Theorem *4.21 of [WhiteheadRussell] p. 117. (Contributed by NM, 5-Aug-1993.) (Revised by NM, 11-Nov-2012.) |
Ref | Expression |
---|---|
bicom | ⊢ ((𝜑 ↔ 𝜓) ↔ (𝜓 ↔ 𝜑)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | bicom1 130 | . 2 ⊢ ((𝜑 ↔ 𝜓) → (𝜓 ↔ 𝜑)) | |
2 | bicom1 130 | . 2 ⊢ ((𝜓 ↔ 𝜑) → (𝜑 ↔ 𝜓)) | |
3 | 1, 2 | impbii 125 | 1 ⊢ ((𝜑 ↔ 𝜓) ↔ (𝜓 ↔ 𝜑)) |
Colors of variables: wff set class |
Syntax hints: ↔ wb 104 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 |
This theorem depends on definitions: df-bi 116 |
This theorem is referenced by: bicomd 140 bibi1i 227 bibi1d 232 ibibr 245 bibif 687 con2bidc 860 con2biddc 865 pm5.17dc 889 bigolden 939 nbbndc 1372 bilukdc 1374 falbitru 1395 3impexpbicom 1414 exists1 2093 eqcom 2139 abeq1 2247 necon2abiddc 2372 necon2bbiddc 2373 necon4bbiddc 2380 ssequn1 3241 axpow3 4096 isocnv 5705 suplocsrlem 7609 uzennn 10202 bezoutlemle 11685 |
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