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Theorem eqreu 2798
Description: A condition which implies existential uniqueness. (Contributed by Mario Carneiro, 2-Oct-2015.)
Hypothesis
Ref Expression
eqreu.1 (𝑥 = 𝐵 → (𝜑𝜓))
Assertion
Ref Expression
eqreu ((𝐵𝐴𝜓 ∧ ∀𝑥𝐴 (𝜑𝑥 = 𝐵)) → ∃!𝑥𝐴 𝜑)
Distinct variable groups:   𝑥,𝐴   𝑥,𝐵   𝜓,𝑥
Allowed substitution hint:   𝜑(𝑥)

Proof of Theorem eqreu
StepHypRef Expression
1 ralbiim 2499 . . . . 5 (∀𝑥𝐴 (𝜑𝑥 = 𝐵) ↔ (∀𝑥𝐴 (𝜑𝑥 = 𝐵) ∧ ∀𝑥𝐴 (𝑥 = 𝐵𝜑)))
2 eqreu.1 . . . . . . 7 (𝑥 = 𝐵 → (𝜑𝜓))
32ceqsralv 2644 . . . . . 6 (𝐵𝐴 → (∀𝑥𝐴 (𝑥 = 𝐵𝜑) ↔ 𝜓))
43anbi2d 452 . . . . 5 (𝐵𝐴 → ((∀𝑥𝐴 (𝜑𝑥 = 𝐵) ∧ ∀𝑥𝐴 (𝑥 = 𝐵𝜑)) ↔ (∀𝑥𝐴 (𝜑𝑥 = 𝐵) ∧ 𝜓)))
51, 4syl5bb 190 . . . 4 (𝐵𝐴 → (∀𝑥𝐴 (𝜑𝑥 = 𝐵) ↔ (∀𝑥𝐴 (𝜑𝑥 = 𝐵) ∧ 𝜓)))
6 reu6i 2797 . . . . 5 ((𝐵𝐴 ∧ ∀𝑥𝐴 (𝜑𝑥 = 𝐵)) → ∃!𝑥𝐴 𝜑)
76ex 113 . . . 4 (𝐵𝐴 → (∀𝑥𝐴 (𝜑𝑥 = 𝐵) → ∃!𝑥𝐴 𝜑))
85, 7sylbird 168 . . 3 (𝐵𝐴 → ((∀𝑥𝐴 (𝜑𝑥 = 𝐵) ∧ 𝜓) → ∃!𝑥𝐴 𝜑))
983impib 1139 . 2 ((𝐵𝐴 ∧ ∀𝑥𝐴 (𝜑𝑥 = 𝐵) ∧ 𝜓) → ∃!𝑥𝐴 𝜑)
1093com23 1147 1 ((𝐵𝐴𝜓 ∧ ∀𝑥𝐴 (𝜑𝑥 = 𝐵)) → ∃!𝑥𝐴 𝜑)
Colors of variables: wff set class
Syntax hints:  wi 4  wa 102  wb 103  w3a 922   = wceq 1287  wcel 1436  wral 2355  ∃!wreu 2357
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-io 663  ax-5 1379  ax-7 1380  ax-gen 1381  ax-ie1 1425  ax-ie2 1426  ax-8 1438  ax-10 1439  ax-11 1440  ax-i12 1441  ax-bndl 1442  ax-4 1443  ax-17 1462  ax-i9 1466  ax-ial 1470  ax-i5r 1471  ax-ext 2067
This theorem depends on definitions:  df-bi 115  df-3an 924  df-tru 1290  df-nf 1393  df-sb 1690  df-eu 1948  df-clab 2072  df-cleq 2078  df-clel 2081  df-nfc 2214  df-ral 2360  df-rex 2361  df-reu 2362  df-v 2617
This theorem is referenced by: (None)
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