Metamath Proof Explorer


Theorem ltnadd

Description: Condition for bounding a natural sum below. (Contributed by Scott Fenton, 21-Jul-2026)

Ref Expression
Assertion ltnadd ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( 𝐴 ∈ ( 𝐵 +no 𝐶 ) ↔ ( ∃ 𝑏𝐵 𝐴 ⊆ ( 𝑏 +no 𝐶 ) ∨ ∃ 𝑐𝐶 𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ) )

Proof

Step Hyp Ref Expression
1 eleq2 ( 𝑥 = 𝐴 → ( ( 𝐵 +no 𝑐 ) ∈ 𝑥 ↔ ( 𝐵 +no 𝑐 ) ∈ 𝐴 ) )
2 1 ralbidv ( 𝑥 = 𝐴 → ( ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝑥 ↔ ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝐴 ) )
3 eleq2 ( 𝑥 = 𝐴 → ( ( 𝑏 +no 𝐶 ) ∈ 𝑥 ↔ ( 𝑏 +no 𝐶 ) ∈ 𝐴 ) )
4 3 ralbidv ( 𝑥 = 𝐴 → ( ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝑥 ↔ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝐴 ) )
5 2 4 anbi12d ( 𝑥 = 𝐴 → ( ( ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝑥 ∧ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝑥 ) ↔ ( ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝐴 ∧ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝐴 ) ) )
6 5 onnminsb ( 𝐴 ∈ On → ( 𝐴 { 𝑥 ∈ On ∣ ( ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝑥 ∧ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝑥 ) } → ¬ ( ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝐴 ∧ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝐴 ) ) )
7 6 3ad2ant1 ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( 𝐴 { 𝑥 ∈ On ∣ ( ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝑥 ∧ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝑥 ) } → ¬ ( ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝐴 ∧ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝐴 ) ) )
8 naddov2 ( ( 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( 𝐵 +no 𝐶 ) = { 𝑥 ∈ On ∣ ( ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝑥 ∧ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝑥 ) } )
9 8 3adant1 ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( 𝐵 +no 𝐶 ) = { 𝑥 ∈ On ∣ ( ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝑥 ∧ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝑥 ) } )
10 9 eleq2d ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( 𝐴 ∈ ( 𝐵 +no 𝐶 ) ↔ 𝐴 { 𝑥 ∈ On ∣ ( ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝑥 ∧ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝑥 ) } ) )
11 simpl1 ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ 𝑏𝐵 ) → 𝐴 ∈ On )
12 onss ( 𝐵 ∈ On → 𝐵 ⊆ On )
13 12 3ad2ant2 ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → 𝐵 ⊆ On )
14 13 sselda ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ 𝑏𝐵 ) → 𝑏 ∈ On )
15 simpl3 ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ 𝑏𝐵 ) → 𝐶 ∈ On )
16 14 15 naddcld ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ 𝑏𝐵 ) → ( 𝑏 +no 𝐶 ) ∈ On )
17 ontri1 ( ( 𝐴 ∈ On ∧ ( 𝑏 +no 𝐶 ) ∈ On ) → ( 𝐴 ⊆ ( 𝑏 +no 𝐶 ) ↔ ¬ ( 𝑏 +no 𝐶 ) ∈ 𝐴 ) )
18 11 16 17 syl2anc ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ 𝑏𝐵 ) → ( 𝐴 ⊆ ( 𝑏 +no 𝐶 ) ↔ ¬ ( 𝑏 +no 𝐶 ) ∈ 𝐴 ) )
19 18 rexbidva ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( ∃ 𝑏𝐵 𝐴 ⊆ ( 𝑏 +no 𝐶 ) ↔ ∃ 𝑏𝐵 ¬ ( 𝑏 +no 𝐶 ) ∈ 𝐴 ) )
20 simpl1 ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ 𝑐𝐶 ) → 𝐴 ∈ On )
21 simpl2 ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ 𝑐𝐶 ) → 𝐵 ∈ On )
22 onss ( 𝐶 ∈ On → 𝐶 ⊆ On )
23 22 3ad2ant3 ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → 𝐶 ⊆ On )
24 23 sselda ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ 𝑐𝐶 ) → 𝑐 ∈ On )
25 21 24 naddcld ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ 𝑐𝐶 ) → ( 𝐵 +no 𝑐 ) ∈ On )
26 ontri1 ( ( 𝐴 ∈ On ∧ ( 𝐵 +no 𝑐 ) ∈ On ) → ( 𝐴 ⊆ ( 𝐵 +no 𝑐 ) ↔ ¬ ( 𝐵 +no 𝑐 ) ∈ 𝐴 ) )
27 20 25 26 syl2anc ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ 𝑐𝐶 ) → ( 𝐴 ⊆ ( 𝐵 +no 𝑐 ) ↔ ¬ ( 𝐵 +no 𝑐 ) ∈ 𝐴 ) )
28 27 rexbidva ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( ∃ 𝑐𝐶 𝐴 ⊆ ( 𝐵 +no 𝑐 ) ↔ ∃ 𝑐𝐶 ¬ ( 𝐵 +no 𝑐 ) ∈ 𝐴 ) )
29 19 28 orbi12d ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( ( ∃ 𝑏𝐵 𝐴 ⊆ ( 𝑏 +no 𝐶 ) ∨ ∃ 𝑐𝐶 𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ↔ ( ∃ 𝑏𝐵 ¬ ( 𝑏 +no 𝐶 ) ∈ 𝐴 ∨ ∃ 𝑐𝐶 ¬ ( 𝐵 +no 𝑐 ) ∈ 𝐴 ) ) )
30 orcom ( ( ¬ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝐴 ∨ ¬ ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝐴 ) ↔ ( ¬ ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝐴 ∨ ¬ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝐴 ) )
31 rexnal ( ∃ 𝑏𝐵 ¬ ( 𝑏 +no 𝐶 ) ∈ 𝐴 ↔ ¬ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝐴 )
32 rexnal ( ∃ 𝑐𝐶 ¬ ( 𝐵 +no 𝑐 ) ∈ 𝐴 ↔ ¬ ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝐴 )
33 31 32 orbi12i ( ( ∃ 𝑏𝐵 ¬ ( 𝑏 +no 𝐶 ) ∈ 𝐴 ∨ ∃ 𝑐𝐶 ¬ ( 𝐵 +no 𝑐 ) ∈ 𝐴 ) ↔ ( ¬ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝐴 ∨ ¬ ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝐴 ) )
34 ianor ( ¬ ( ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝐴 ∧ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝐴 ) ↔ ( ¬ ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝐴 ∨ ¬ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝐴 ) )
35 30 33 34 3bitr4i ( ( ∃ 𝑏𝐵 ¬ ( 𝑏 +no 𝐶 ) ∈ 𝐴 ∨ ∃ 𝑐𝐶 ¬ ( 𝐵 +no 𝑐 ) ∈ 𝐴 ) ↔ ¬ ( ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝐴 ∧ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝐴 ) )
36 29 35 bitrdi ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( ( ∃ 𝑏𝐵 𝐴 ⊆ ( 𝑏 +no 𝐶 ) ∨ ∃ 𝑐𝐶 𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ↔ ¬ ( ∀ 𝑐𝐶 ( 𝐵 +no 𝑐 ) ∈ 𝐴 ∧ ∀ 𝑏𝐵 ( 𝑏 +no 𝐶 ) ∈ 𝐴 ) ) )
37 7 10 36 3imtr4d ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( 𝐴 ∈ ( 𝐵 +no 𝐶 ) → ( ∃ 𝑏𝐵 𝐴 ⊆ ( 𝑏 +no 𝐶 ) ∨ ∃ 𝑐𝐶 𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ) )
38 simprr ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑏𝐵𝐴 ⊆ ( 𝑏 +no 𝐶 ) ) ) → 𝐴 ⊆ ( 𝑏 +no 𝐶 ) )
39 simprl ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑏𝐵𝐴 ⊆ ( 𝑏 +no 𝐶 ) ) ) → 𝑏𝐵 )
40 14 adantrr ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑏𝐵𝐴 ⊆ ( 𝑏 +no 𝐶 ) ) ) → 𝑏 ∈ On )
41 simpl2 ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑏𝐵𝐴 ⊆ ( 𝑏 +no 𝐶 ) ) ) → 𝐵 ∈ On )
42 simpl3 ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑏𝐵𝐴 ⊆ ( 𝑏 +no 𝐶 ) ) ) → 𝐶 ∈ On )
43 naddel1 ( ( 𝑏 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( 𝑏𝐵 ↔ ( 𝑏 +no 𝐶 ) ∈ ( 𝐵 +no 𝐶 ) ) )
44 40 41 42 43 syl3anc ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑏𝐵𝐴 ⊆ ( 𝑏 +no 𝐶 ) ) ) → ( 𝑏𝐵 ↔ ( 𝑏 +no 𝐶 ) ∈ ( 𝐵 +no 𝐶 ) ) )
45 39 44 mpbid ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑏𝐵𝐴 ⊆ ( 𝑏 +no 𝐶 ) ) ) → ( 𝑏 +no 𝐶 ) ∈ ( 𝐵 +no 𝐶 ) )
46 simpl1 ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑏𝐵𝐴 ⊆ ( 𝑏 +no 𝐶 ) ) ) → 𝐴 ∈ On )
47 naddcl ( ( 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( 𝐵 +no 𝐶 ) ∈ On )
48 47 3adant1 ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( 𝐵 +no 𝐶 ) ∈ On )
49 48 adantr ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑏𝐵𝐴 ⊆ ( 𝑏 +no 𝐶 ) ) ) → ( 𝐵 +no 𝐶 ) ∈ On )
50 ontr2 ( ( 𝐴 ∈ On ∧ ( 𝐵 +no 𝐶 ) ∈ On ) → ( ( 𝐴 ⊆ ( 𝑏 +no 𝐶 ) ∧ ( 𝑏 +no 𝐶 ) ∈ ( 𝐵 +no 𝐶 ) ) → 𝐴 ∈ ( 𝐵 +no 𝐶 ) ) )
51 46 49 50 syl2anc ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑏𝐵𝐴 ⊆ ( 𝑏 +no 𝐶 ) ) ) → ( ( 𝐴 ⊆ ( 𝑏 +no 𝐶 ) ∧ ( 𝑏 +no 𝐶 ) ∈ ( 𝐵 +no 𝐶 ) ) → 𝐴 ∈ ( 𝐵 +no 𝐶 ) ) )
52 38 45 51 mp2and ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑏𝐵𝐴 ⊆ ( 𝑏 +no 𝐶 ) ) ) → 𝐴 ∈ ( 𝐵 +no 𝐶 ) )
53 52 rexlimdvaa ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( ∃ 𝑏𝐵 𝐴 ⊆ ( 𝑏 +no 𝐶 ) → 𝐴 ∈ ( 𝐵 +no 𝐶 ) ) )
54 simprr ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑐𝐶𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ) → 𝐴 ⊆ ( 𝐵 +no 𝑐 ) )
55 simprl ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑐𝐶𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ) → 𝑐𝐶 )
56 24 adantrr ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑐𝐶𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ) → 𝑐 ∈ On )
57 simpl3 ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑐𝐶𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ) → 𝐶 ∈ On )
58 simpl2 ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑐𝐶𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ) → 𝐵 ∈ On )
59 naddel2 ( ( 𝑐 ∈ On ∧ 𝐶 ∈ On ∧ 𝐵 ∈ On ) → ( 𝑐𝐶 ↔ ( 𝐵 +no 𝑐 ) ∈ ( 𝐵 +no 𝐶 ) ) )
60 56 57 58 59 syl3anc ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑐𝐶𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ) → ( 𝑐𝐶 ↔ ( 𝐵 +no 𝑐 ) ∈ ( 𝐵 +no 𝐶 ) ) )
61 55 60 mpbid ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑐𝐶𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ) → ( 𝐵 +no 𝑐 ) ∈ ( 𝐵 +no 𝐶 ) )
62 simpl1 ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑐𝐶𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ) → 𝐴 ∈ On )
63 48 adantr ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑐𝐶𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ) → ( 𝐵 +no 𝐶 ) ∈ On )
64 ontr2 ( ( 𝐴 ∈ On ∧ ( 𝐵 +no 𝐶 ) ∈ On ) → ( ( 𝐴 ⊆ ( 𝐵 +no 𝑐 ) ∧ ( 𝐵 +no 𝑐 ) ∈ ( 𝐵 +no 𝐶 ) ) → 𝐴 ∈ ( 𝐵 +no 𝐶 ) ) )
65 62 63 64 syl2anc ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑐𝐶𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ) → ( ( 𝐴 ⊆ ( 𝐵 +no 𝑐 ) ∧ ( 𝐵 +no 𝑐 ) ∈ ( 𝐵 +no 𝐶 ) ) → 𝐴 ∈ ( 𝐵 +no 𝐶 ) ) )
66 54 61 65 mp2and ( ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) ∧ ( 𝑐𝐶𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ) → 𝐴 ∈ ( 𝐵 +no 𝐶 ) )
67 66 rexlimdvaa ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( ∃ 𝑐𝐶 𝐴 ⊆ ( 𝐵 +no 𝑐 ) → 𝐴 ∈ ( 𝐵 +no 𝐶 ) ) )
68 53 67 jaod ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( ( ∃ 𝑏𝐵 𝐴 ⊆ ( 𝑏 +no 𝐶 ) ∨ ∃ 𝑐𝐶 𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) → 𝐴 ∈ ( 𝐵 +no 𝐶 ) ) )
69 37 68 impbid ( ( 𝐴 ∈ On ∧ 𝐵 ∈ On ∧ 𝐶 ∈ On ) → ( 𝐴 ∈ ( 𝐵 +no 𝐶 ) ↔ ( ∃ 𝑏𝐵 𝐴 ⊆ ( 𝑏 +no 𝐶 ) ∨ ∃ 𝑐𝐶 𝐴 ⊆ ( 𝐵 +no 𝑐 ) ) ) )