Theorem noetasuplem1

Description: Lemma for noeta . Establish that our final surreal really is a surreal. (Contributed by Scott Fenton, 6-Dec-2021)

	Ref	Expression
Hypotheses	noetasuplem.1	⊢ 𝑆 = if ( ∃ 𝑥 ∈ 𝐴 ∀ 𝑦 ∈ 𝐴 ¬ 𝑥 <s 𝑦 , ( ( ℩ 𝑥 ∈ 𝐴 ∀ 𝑦 ∈ 𝐴 ¬ 𝑥 <s 𝑦 ) ∪ { ⟨ dom ( ℩ 𝑥 ∈ 𝐴 ∀ 𝑦 ∈ 𝐴 ¬ 𝑥 <s 𝑦 ) , 2o ⟩ } ) , ( 𝑔 ∈ { 𝑦 ∣ ∃ 𝑢 ∈ 𝐴 ( 𝑦 ∈ dom 𝑢 ∧ ∀ 𝑣 ∈ 𝐴 ( ¬ 𝑣 <s 𝑢 → ( 𝑢 ↾ suc 𝑦 ) = ( 𝑣 ↾ suc 𝑦 ) ) ) } ↦ ( ℩ 𝑥 ∃ 𝑢 ∈ 𝐴 ( 𝑔 ∈ dom 𝑢 ∧ ∀ 𝑣 ∈ 𝐴 ( ¬ 𝑣 <s 𝑢 → ( 𝑢 ↾ suc 𝑔 ) = ( 𝑣 ↾ suc 𝑔 ) ) ∧ ( 𝑢 ‘ 𝑔 ) = 𝑥 ) ) ) )
	noetasuplem.2	⊢ 𝑍 = ( 𝑆 ∪ ( ( suc ∪ ( bday “ 𝐵 ) ∖ dom 𝑆 ) × { 1o } ) )
Assertion	noetasuplem1	⊢ ( ( 𝐴 ⊆ No ∧ 𝐴 ∈ V ∧ 𝐵 ∈ V ) → 𝑍 ∈ No )

Proof

Step	Hyp	Ref	Expression
1		noetasuplem.1	⊢ 𝑆 = if ( ∃ 𝑥 ∈ 𝐴 ∀ 𝑦 ∈ 𝐴 ¬ 𝑥 <s 𝑦 , ( ( ℩ 𝑥 ∈ 𝐴 ∀ 𝑦 ∈ 𝐴 ¬ 𝑥 <s 𝑦 ) ∪ { ⟨ dom ( ℩ 𝑥 ∈ 𝐴 ∀ 𝑦 ∈ 𝐴 ¬ 𝑥 <s 𝑦 ) , 2o ⟩ } ) , ( 𝑔 ∈ { 𝑦 ∣ ∃ 𝑢 ∈ 𝐴 ( 𝑦 ∈ dom 𝑢 ∧ ∀ 𝑣 ∈ 𝐴 ( ¬ 𝑣 <s 𝑢 → ( 𝑢 ↾ suc 𝑦 ) = ( 𝑣 ↾ suc 𝑦 ) ) ) } ↦ ( ℩ 𝑥 ∃ 𝑢 ∈ 𝐴 ( 𝑔 ∈ dom 𝑢 ∧ ∀ 𝑣 ∈ 𝐴 ( ¬ 𝑣 <s 𝑢 → ( 𝑢 ↾ suc 𝑔 ) = ( 𝑣 ↾ suc 𝑔 ) ) ∧ ( 𝑢 ‘ 𝑔 ) = 𝑥 ) ) ) )
2		noetasuplem.2	⊢ 𝑍 = ( 𝑆 ∪ ( ( suc ∪ ( bday “ 𝐵 ) ∖ dom 𝑆 ) × { 1o } ) )
3	1	nosupno	⊢ ( ( 𝐴 ⊆ No ∧ 𝐴 ∈ V ) → 𝑆 ∈ No )
4	3	3adant3	⊢ ( ( 𝐴 ⊆ No ∧ 𝐴 ∈ V ∧ 𝐵 ∈ V ) → 𝑆 ∈ No )
5		bdayimaon	⊢ ( 𝐵 ∈ V → suc ∪ ( bday “ 𝐵 ) ∈ On )
6	5	3ad2ant3	⊢ ( ( 𝐴 ⊆ No ∧ 𝐴 ∈ V ∧ 𝐵 ∈ V ) → suc ∪ ( bday “ 𝐵 ) ∈ On )
7		1oex	⊢ 1o ∈ V
8	7	prid1	⊢ 1o ∈ { 1o , 2o }
9	8	noextendseq	⊢ ( ( 𝑆 ∈ No ∧ suc ∪ ( bday “ 𝐵 ) ∈ On ) → ( 𝑆 ∪ ( ( suc ∪ ( bday “ 𝐵 ) ∖ dom 𝑆 ) × { 1o } ) ) ∈ No )
10	4 6 9	syl2anc	⊢ ( ( 𝐴 ⊆ No ∧ 𝐴 ∈ V ∧ 𝐵 ∈ V ) → ( 𝑆 ∪ ( ( suc ∪ ( bday “ 𝐵 ) ∖ dom 𝑆 ) × { 1o } ) ) ∈ No )
11	2 10	eqeltrid	⊢ ( ( 𝐴 ⊆ No ∧ 𝐴 ∈ V ∧ 𝐵 ∈ V ) → 𝑍 ∈ No )