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Mirrors > Home > ILE Home > Th. List > eqeq12 | GIF version |
Description: Equality relationship among 4 classes. (Contributed by NM, 3-Aug-1994.) |
Ref | Expression |
---|---|
eqeq12 | ⊢ ((𝐴 = 𝐵 ∧ 𝐶 = 𝐷) → (𝐴 = 𝐶 ↔ 𝐵 = 𝐷)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eqeq1 2101 | . 2 ⊢ (𝐴 = 𝐵 → (𝐴 = 𝐶 ↔ 𝐵 = 𝐶)) | |
2 | eqeq2 2104 | . 2 ⊢ (𝐶 = 𝐷 → (𝐵 = 𝐶 ↔ 𝐵 = 𝐷)) | |
3 | 1, 2 | sylan9bb 451 | 1 ⊢ ((𝐴 = 𝐵 ∧ 𝐶 = 𝐷) → (𝐴 = 𝐶 ↔ 𝐵 = 𝐷)) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ∧ wa 103 ↔ wb 104 = wceq 1296 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-5 1388 ax-gen 1390 ax-4 1452 ax-17 1471 ax-ext 2077 |
This theorem depends on definitions: df-bi 116 df-cleq 2088 |
This theorem is referenced by: eqeq12i 2108 eqeq12d 2109 eqeqan12d 2110 funopg 5082 tfri3 6170 th3qlem1 6434 xpdom2 6627 xrlttri3 9366 bcn1 10281 summodc 10926 |
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