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Theorem df3o3 43304
Description: Ordinal 3, fully expanded. (Contributed by RP, 8-Jul-2021.)
Assertion
Ref Expression
df3o3 3o = {∅, {∅}, {∅, {∅}}}

Proof of Theorem df3o3
StepHypRef Expression
1 df-3o 8507 . 2 3o = suc 2o
2 df2o2 8514 . . . 4 2o = {∅, {∅}}
32sneqi 4642 . . . 4 {2o} = {{∅, {∅}}}
42, 3uneq12i 4176 . . 3 (2o ∪ {2o}) = ({∅, {∅}} ∪ {{∅, {∅}}})
5 df-suc 6392 . . 3 suc 2o = (2o ∪ {2o})
6 df-tp 4636 . . 3 {∅, {∅}, {∅, {∅}}} = ({∅, {∅}} ∪ {{∅, {∅}}})
74, 5, 63eqtr4i 2773 . 2 suc 2o = {∅, {∅}, {∅, {∅}}}
81, 7eqtri 2763 1 3o = {∅, {∅}, {∅, {∅}}}
Colors of variables: wff setvar class
Syntax hints:   = wceq 1537  cun 3961  c0 4339  {csn 4631  {cpr 4633  {ctp 4635  suc csuc 6388  2oc2o 8499  3oc3o 8500
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1792  ax-4 1806  ax-5 1908  ax-6 1965  ax-7 2005  ax-8 2108  ax-9 2116  ax-ext 2706
This theorem depends on definitions:  df-bi 207  df-an 396  df-or 848  df-tru 1540  df-fal 1550  df-ex 1777  df-sb 2063  df-clab 2713  df-cleq 2727  df-clel 2814  df-v 3480  df-dif 3966  df-un 3968  df-nul 4340  df-sn 4632  df-pr 4634  df-tp 4636  df-suc 6392  df-1o 8505  df-2o 8506  df-3o 8507
This theorem is referenced by: (None)
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