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Theorem tfr1 8020
 Description: Principle of Transfinite Recursion, part 1 of 3. Theorem 7.41(1) of [TakeutiZaring] p. 47. We start with an arbitrary class 𝐺, normally a function, and define a class 𝐴 of all "acceptable" functions. The final function we're interested in is the union 𝐹 = recs(𝐺) of them. 𝐹 is then said to be defined by transfinite recursion. The purpose of the 3 parts of this theorem is to demonstrate properties of 𝐹. In this first part we show that 𝐹 is a function whose domain is all ordinal numbers. (Contributed by NM, 17-Aug-1994.) (Revised by Mario Carneiro, 18-Jan-2015.)
Hypothesis
Ref Expression
tfr.1 𝐹 = recs(𝐺)
Assertion
Ref Expression
tfr1 𝐹 Fn On

Proof of Theorem tfr1
Dummy variables 𝑥 𝑓 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 eqid 2801 . . . 4 {𝑓 ∣ ∃𝑥 ∈ On (𝑓 Fn 𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) = (𝐺‘(𝑓𝑦)))} = {𝑓 ∣ ∃𝑥 ∈ On (𝑓 Fn 𝑥 ∧ ∀𝑦𝑥 (𝑓𝑦) = (𝐺‘(𝑓𝑦)))}
21tfrlem7 8006 . . 3 Fun recs(𝐺)
31tfrlem14 8014 . . 3 dom recs(𝐺) = On
4 df-fn 6331 . . 3 (recs(𝐺) Fn On ↔ (Fun recs(𝐺) ∧ dom recs(𝐺) = On))
52, 3, 4mpbir2an 710 . 2 recs(𝐺) Fn On
6 tfr.1 . . 3 𝐹 = recs(𝐺)
76fneq1i 6424 . 2 (𝐹 Fn On ↔ recs(𝐺) Fn On)
85, 7mpbir 234 1 𝐹 Fn On
 Colors of variables: wff setvar class Syntax hints:   ∧ wa 399   = wceq 1538  {cab 2779  ∀wral 3109  ∃wrex 3110  dom cdm 5523   ↾ cres 5525  Oncon0 6163  Fun wfun 6322   Fn wfn 6323  ‘cfv 6328  recscrecs 7994 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1911  ax-6 1970  ax-7 2015  ax-8 2114  ax-9 2122  ax-10 2143  ax-11 2159  ax-12 2176  ax-ext 2773  ax-rep 5157  ax-sep 5170  ax-nul 5177  ax-pow 5234  ax-pr 5298  ax-un 7445 This theorem depends on definitions:  df-bi 210  df-an 400  df-or 845  df-3or 1085  df-3an 1086  df-tru 1541  df-ex 1782  df-nf 1786  df-sb 2070  df-mo 2601  df-eu 2632  df-clab 2780  df-cleq 2794  df-clel 2873  df-nfc 2941  df-ne 2991  df-ral 3114  df-rex 3115  df-reu 3116  df-rab 3118  df-v 3446  df-sbc 3724  df-csb 3832  df-dif 3887  df-un 3889  df-in 3891  df-ss 3901  df-pss 3903  df-nul 4247  df-if 4429  df-sn 4529  df-pr 4531  df-tp 4533  df-op 4535  df-uni 4804  df-iun 4886  df-br 5034  df-opab 5096  df-mpt 5114  df-tr 5140  df-id 5428  df-eprel 5433  df-po 5442  df-so 5443  df-fr 5482  df-we 5484  df-xp 5529  df-rel 5530  df-cnv 5531  df-co 5532  df-dm 5533  df-rn 5534  df-res 5535  df-ima 5536  df-pred 6120  df-ord 6166  df-on 6167  df-suc 6169  df-iota 6287  df-fun 6330  df-fn 6331  df-f 6332  df-f1 6333  df-fo 6334  df-f1o 6335  df-fv 6336  df-wrecs 7934  df-recs 7995 This theorem is referenced by:  tfr2  8021  tfr3  8022  recsfnon  8026  rdgfnon  8041  dfac8alem  9444  dfac12lem1  9558  dfac12lem2  9559  zorn2lem1  9911  zorn2lem2  9912  zorn2lem4  9914  zorn2lem5  9915  zorn2lem6  9916  zorn2lem7  9917  ttukeylem3  9926  ttukeylem5  9928  ttukeylem6  9929  madeval  33403  dnnumch1  39985  dnnumch3lem  39987  dnnumch3  39988  aomclem6  40000
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