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Theorem dfatco 43324
 Description: The predicate "defined at" for a function composition. (Contributed by AV, 8-Sep-2022.)
Assertion
Ref Expression
dfatco ((𝐺 defAt 𝑋𝐹 defAt (𝐺''''𝑋)) → (𝐹𝐺) defAt 𝑋)

Proof of Theorem dfatco
Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 dfatcolem 43323 . . . 4 ((𝐺 defAt 𝑋𝐹 defAt (𝐺''''𝑋)) → ∃!𝑦 𝑋(𝐹𝐺)𝑦)
2 euex 2660 . . . 4 (∃!𝑦 𝑋(𝐹𝐺)𝑦 → ∃𝑦 𝑋(𝐹𝐺)𝑦)
31, 2syl 17 . . 3 ((𝐺 defAt 𝑋𝐹 defAt (𝐺''''𝑋)) → ∃𝑦 𝑋(𝐹𝐺)𝑦)
4 df-dm 5564 . . . . 5 dom (𝐹𝐺) = {𝑥 ∣ ∃𝑦 𝑥(𝐹𝐺)𝑦}
54eleq2i 2909 . . . 4 (𝑋 ∈ dom (𝐹𝐺) ↔ 𝑋 ∈ {𝑥 ∣ ∃𝑦 𝑥(𝐹𝐺)𝑦})
6 df-dfat 43187 . . . . . . 7 (𝐺 defAt 𝑋 ↔ (𝑋 ∈ dom 𝐺 ∧ Fun (𝐺 ↾ {𝑋})))
76simplbi 498 . . . . . 6 (𝐺 defAt 𝑋𝑋 ∈ dom 𝐺)
87adantr 481 . . . . 5 ((𝐺 defAt 𝑋𝐹 defAt (𝐺''''𝑋)) → 𝑋 ∈ dom 𝐺)
9 breq1 5066 . . . . . . 7 (𝑥 = 𝑋 → (𝑥(𝐹𝐺)𝑦𝑋(𝐹𝐺)𝑦))
109exbidv 1915 . . . . . 6 (𝑥 = 𝑋 → (∃𝑦 𝑥(𝐹𝐺)𝑦 ↔ ∃𝑦 𝑋(𝐹𝐺)𝑦))
1110elabg 3670 . . . . 5 (𝑋 ∈ dom 𝐺 → (𝑋 ∈ {𝑥 ∣ ∃𝑦 𝑥(𝐹𝐺)𝑦} ↔ ∃𝑦 𝑋(𝐹𝐺)𝑦))
128, 11syl 17 . . . 4 ((𝐺 defAt 𝑋𝐹 defAt (𝐺''''𝑋)) → (𝑋 ∈ {𝑥 ∣ ∃𝑦 𝑥(𝐹𝐺)𝑦} ↔ ∃𝑦 𝑋(𝐹𝐺)𝑦))
135, 12syl5bb 284 . . 3 ((𝐺 defAt 𝑋𝐹 defAt (𝐺''''𝑋)) → (𝑋 ∈ dom (𝐹𝐺) ↔ ∃𝑦 𝑋(𝐹𝐺)𝑦))
143, 13mpbird 258 . 2 ((𝐺 defAt 𝑋𝐹 defAt (𝐺''''𝑋)) → 𝑋 ∈ dom (𝐹𝐺))
15 dfdfat2 43196 . 2 ((𝐹𝐺) defAt 𝑋 ↔ (𝑋 ∈ dom (𝐹𝐺) ∧ ∃!𝑦 𝑋(𝐹𝐺)𝑦))
1614, 1, 15sylanbrc 583 1 ((𝐺 defAt 𝑋𝐹 defAt (𝐺''''𝑋)) → (𝐹𝐺) defAt 𝑋)
 Colors of variables: wff setvar class Syntax hints:   → wi 4   ↔ wb 207   ∧ wa 396   = wceq 1530  ∃wex 1773   ∈ wcel 2107  ∃!weu 2651  {cab 2804  {csn 4564   class class class wbr 5063  dom cdm 5554   ↾ cres 5556   ∘ ccom 5558  Fun wfun 6346   defAt wdfat 43184  ''''cafv2 43276 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1789  ax-4 1803  ax-5 1904  ax-6 1963  ax-7 2008  ax-8 2109  ax-9 2117  ax-10 2138  ax-11 2153  ax-12 2169  ax-ext 2798  ax-sep 5200  ax-nul 5207  ax-pow 5263  ax-pr 5326 This theorem depends on definitions:  df-bi 208  df-an 397  df-or 844  df-3an 1083  df-tru 1533  df-ex 1774  df-nf 1778  df-sb 2063  df-mo 2620  df-eu 2652  df-clab 2805  df-cleq 2819  df-clel 2898  df-nfc 2968  df-ral 3148  df-rex 3149  df-rab 3152  df-v 3502  df-sbc 3777  df-dif 3943  df-un 3945  df-in 3947  df-ss 3956  df-nul 4296  df-if 4471  df-sn 4565  df-pr 4567  df-op 4571  df-uni 4838  df-br 5064  df-opab 5126  df-id 5459  df-xp 5560  df-rel 5561  df-cnv 5562  df-co 5563  df-dm 5564  df-res 5566  df-iota 6312  df-fun 6354  df-fn 6355  df-dfat 43187  df-afv2 43277 This theorem is referenced by:  afv2co2  43325
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