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Theorem elabrexg 39728
 Description: Elementhood in an image set. (Contributed by Glauco Siliprandi, 11-Dec-2019.)
Assertion
Ref Expression
elabrexg ((𝑥𝐴𝐵𝑉) → 𝐵 ∈ {𝑦 ∣ ∃𝑥𝐴 𝑦 = 𝐵})
Distinct variable groups:   𝑥,𝐴,𝑦   𝑦,𝐵
Allowed substitution hints:   𝐵(𝑥)   𝑉(𝑥,𝑦)

Proof of Theorem elabrexg
Dummy variable 𝑧 is distinct from all other variables.
StepHypRef Expression
1 tru 1635 . . . . 5
2 csbeq1a 3691 . . . . . . . 8 (𝑥 = 𝑧𝐵 = 𝑧 / 𝑥𝐵)
32equcoms 2105 . . . . . . 7 (𝑧 = 𝑥𝐵 = 𝑧 / 𝑥𝐵)
4 a1tru 1648 . . . . . . 7 (𝑧 = 𝑥 → ⊤)
53, 42thd 255 . . . . . 6 (𝑧 = 𝑥 → (𝐵 = 𝑧 / 𝑥𝐵 ↔ ⊤))
65rspcev 3460 . . . . 5 ((𝑥𝐴 ∧ ⊤) → ∃𝑧𝐴 𝐵 = 𝑧 / 𝑥𝐵)
71, 6mpan2 671 . . . 4 (𝑥𝐴 → ∃𝑧𝐴 𝐵 = 𝑧 / 𝑥𝐵)
87adantr 466 . . 3 ((𝑥𝐴𝐵𝑉) → ∃𝑧𝐴 𝐵 = 𝑧 / 𝑥𝐵)
9 eqeq1 2775 . . . . . 6 (𝑦 = 𝐵 → (𝑦 = 𝑧 / 𝑥𝐵𝐵 = 𝑧 / 𝑥𝐵))
109rexbidv 3200 . . . . 5 (𝑦 = 𝐵 → (∃𝑧𝐴 𝑦 = 𝑧 / 𝑥𝐵 ↔ ∃𝑧𝐴 𝐵 = 𝑧 / 𝑥𝐵))
1110elabg 3502 . . . 4 (𝐵𝑉 → (𝐵 ∈ {𝑦 ∣ ∃𝑧𝐴 𝑦 = 𝑧 / 𝑥𝐵} ↔ ∃𝑧𝐴 𝐵 = 𝑧 / 𝑥𝐵))
1211adantl 467 . . 3 ((𝑥𝐴𝐵𝑉) → (𝐵 ∈ {𝑦 ∣ ∃𝑧𝐴 𝑦 = 𝑧 / 𝑥𝐵} ↔ ∃𝑧𝐴 𝐵 = 𝑧 / 𝑥𝐵))
138, 12mpbird 247 . 2 ((𝑥𝐴𝐵𝑉) → 𝐵 ∈ {𝑦 ∣ ∃𝑧𝐴 𝑦 = 𝑧 / 𝑥𝐵})
14 nfv 1995 . . . 4 𝑧 𝑦 = 𝐵
15 nfcsb1v 3698 . . . . 5 𝑥𝑧 / 𝑥𝐵
1615nfeq2 2929 . . . 4 𝑥 𝑦 = 𝑧 / 𝑥𝐵
172eqeq2d 2781 . . . 4 (𝑥 = 𝑧 → (𝑦 = 𝐵𝑦 = 𝑧 / 𝑥𝐵))
1814, 16, 17cbvrex 3317 . . 3 (∃𝑥𝐴 𝑦 = 𝐵 ↔ ∃𝑧𝐴 𝑦 = 𝑧 / 𝑥𝐵)
1918abbii 2888 . 2 {𝑦 ∣ ∃𝑥𝐴 𝑦 = 𝐵} = {𝑦 ∣ ∃𝑧𝐴 𝑦 = 𝑧 / 𝑥𝐵}
2013, 19syl6eleqr 2861 1 ((𝑥𝐴𝐵𝑉) → 𝐵 ∈ {𝑦 ∣ ∃𝑥𝐴 𝑦 = 𝐵})
 Colors of variables: wff setvar class Syntax hints:   → wi 4   ↔ wb 196   ∧ wa 382   = wceq 1631  ⊤wtru 1632   ∈ wcel 2145  {cab 2757  ∃wrex 3062  ⦋csb 3682 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1870  ax-4 1885  ax-5 1991  ax-6 2057  ax-7 2093  ax-9 2154  ax-10 2174  ax-11 2190  ax-12 2203  ax-13 2408  ax-ext 2751 This theorem depends on definitions:  df-bi 197  df-an 383  df-or 837  df-tru 1634  df-ex 1853  df-nf 1858  df-sb 2050  df-clab 2758  df-cleq 2764  df-clel 2767  df-nfc 2902  df-ral 3066  df-rex 3067  df-v 3353  df-sbc 3588  df-csb 3683 This theorem is referenced by:  upbdrech  40036  ssfiunibd  40040
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