Theorem n4cyclfrgra 26545

Description: There is no 4-cycle in a friendship graph, see Proposition 1(a) of [MertziosUnger] p. 153 : "A friendship graph G contains no C4 as a subgraph ...". (Contributed by Alexander van der Vekens, 19-Nov-2017.)

Assertion

Ref	Expression
n4cyclfrgra	⊢ ((𝑉 FriendGrph 𝐸 ∧ 𝐹(𝑉 Cycles 𝐸)𝑃) → (#‘𝐹) ≠ 4)

Proof of Theorem n4cyclfrgra

Dummy variables 𝑎 𝑏 𝑐 𝑑 𝑘 𝑙 𝑥 are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		frisusgra 26519	. . . 4 ⊢ (𝑉 FriendGrph 𝐸 → 𝑉 USGrph 𝐸)
2		4cycl4dv4e 26196	. . . . . . . 8 ⊢ ((𝑉 USGrph 𝐸 ∧ 𝐹(𝑉 Cycles 𝐸)𝑃 ∧ (#‘𝐹) = 4) → ∃𝑎 ∈ 𝑉 ∃𝑏 ∈ 𝑉 ∃𝑐 ∈ 𝑉 ∃𝑑 ∈ 𝑉 ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑))))
3		frisusgrapr 26518	. . . . . . . . . . . . 13 ⊢ (𝑉 FriendGrph 𝐸 → (𝑉 USGrph 𝐸 ∧ ∀𝑘 ∈ 𝑉 ∀𝑙 ∈ (𝑉 ∖ {𝑘})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑘}, {𝑥, 𝑙}} ⊆ ran 𝐸))
4		simpl 472	. . . . . . . . . . . . . . . . . . . 20 ⊢ ((𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉) → 𝑐 ∈ 𝑉)
5	4	adantl 481	. . . . . . . . . . . . . . . . . . 19 ⊢ (((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) → 𝑐 ∈ 𝑉)
6	5	adantr 480	. . . . . . . . . . . . . . . . . 18 ⊢ ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → 𝑐 ∈ 𝑉)
7		necom 2835	. . . . . . . . . . . . . . . . . . . . . 22 ⊢ (𝑎 ≠ 𝑐 ↔ 𝑐 ≠ 𝑎)
8	7	biimpi 205	. . . . . . . . . . . . . . . . . . . . 21 ⊢ (𝑎 ≠ 𝑐 → 𝑐 ≠ 𝑎)
9	8	3ad2ant2 1076	. . . . . . . . . . . . . . . . . . . 20 ⊢ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) → 𝑐 ≠ 𝑎)
10	9	ad2antrl 760	. . . . . . . . . . . . . . . . . . 19 ⊢ (((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑))) → 𝑐 ≠ 𝑎)
11	10	adantl 481	. . . . . . . . . . . . . . . . . 18 ⊢ ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → 𝑐 ≠ 𝑎)
12		eldifsn 4260	. . . . . . . . . . . . . . . . . 18 ⊢ (𝑐 ∈ (𝑉 ∖ {𝑎}) ↔ (𝑐 ∈ 𝑉 ∧ 𝑐 ≠ 𝑎))
13	6, 11, 12	sylanbrc 695	. . . . . . . . . . . . . . . . 17 ⊢ ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → 𝑐 ∈ (𝑉 ∖ {𝑎}))
14		sneq 4135	. . . . . . . . . . . . . . . . . . . . . . 23 ⊢ (𝑘 = 𝑎 → {𝑘} = {𝑎})
15	14	difeq2d 3690	. . . . . . . . . . . . . . . . . . . . . 22 ⊢ (𝑘 = 𝑎 → (𝑉 ∖ {𝑘}) = (𝑉 ∖ {𝑎}))
16		preq2 4213	. . . . . . . . . . . . . . . . . . . . . . . . 25 ⊢ (𝑘 = 𝑎 → {𝑥, 𝑘} = {𝑥, 𝑎})
17	16	preq1d 4218	. . . . . . . . . . . . . . . . . . . . . . . 24 ⊢ (𝑘 = 𝑎 → {{𝑥, 𝑘}, {𝑥, 𝑙}} = {{𝑥, 𝑎}, {𝑥, 𝑙}})
18	17	sseq1d 3595	. . . . . . . . . . . . . . . . . . . . . . 23 ⊢ (𝑘 = 𝑎 → ({{𝑥, 𝑘}, {𝑥, 𝑙}} ⊆ ran 𝐸 ↔ {{𝑥, 𝑎}, {𝑥, 𝑙}} ⊆ ran 𝐸))
19	18	reubidv 3103	. . . . . . . . . . . . . . . . . . . . . 22 ⊢ (𝑘 = 𝑎 → (∃!𝑥 ∈ 𝑉 {{𝑥, 𝑘}, {𝑥, 𝑙}} ⊆ ran 𝐸 ↔ ∃!𝑥 ∈ 𝑉 {{𝑥, 𝑎}, {𝑥, 𝑙}} ⊆ ran 𝐸))
20	15, 19	raleqbidv 3129	. . . . . . . . . . . . . . . . . . . . 21 ⊢ (𝑘 = 𝑎 → (∀𝑙 ∈ (𝑉 ∖ {𝑘})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑘}, {𝑥, 𝑙}} ⊆ ran 𝐸 ↔ ∀𝑙 ∈ (𝑉 ∖ {𝑎})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑎}, {𝑥, 𝑙}} ⊆ ran 𝐸))
21	20	rspcv 3278	. . . . . . . . . . . . . . . . . . . 20 ⊢ (𝑎 ∈ 𝑉 → (∀𝑘 ∈ 𝑉 ∀𝑙 ∈ (𝑉 ∖ {𝑘})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑘}, {𝑥, 𝑙}} ⊆ ran 𝐸 → ∀𝑙 ∈ (𝑉 ∖ {𝑎})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑎}, {𝑥, 𝑙}} ⊆ ran 𝐸))
22	21	adantr 480	. . . . . . . . . . . . . . . . . . 19 ⊢ ((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) → (∀𝑘 ∈ 𝑉 ∀𝑙 ∈ (𝑉 ∖ {𝑘})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑘}, {𝑥, 𝑙}} ⊆ ran 𝐸 → ∀𝑙 ∈ (𝑉 ∖ {𝑎})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑎}, {𝑥, 𝑙}} ⊆ ran 𝐸))
23	22	adantr 480	. . . . . . . . . . . . . . . . . 18 ⊢ (((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) → (∀𝑘 ∈ 𝑉 ∀𝑙 ∈ (𝑉 ∖ {𝑘})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑘}, {𝑥, 𝑙}} ⊆ ran 𝐸 → ∀𝑙 ∈ (𝑉 ∖ {𝑎})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑎}, {𝑥, 𝑙}} ⊆ ran 𝐸))
24	23	adantr 480	. . . . . . . . . . . . . . . . 17 ⊢ ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → (∀𝑘 ∈ 𝑉 ∀𝑙 ∈ (𝑉 ∖ {𝑘})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑘}, {𝑥, 𝑙}} ⊆ ran 𝐸 → ∀𝑙 ∈ (𝑉 ∖ {𝑎})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑎}, {𝑥, 𝑙}} ⊆ ran 𝐸))
25		preq2 4213	. . . . . . . . . . . . . . . . . . . . 21 ⊢ (𝑙 = 𝑐 → {𝑥, 𝑙} = {𝑥, 𝑐})
26	25	preq2d 4219	. . . . . . . . . . . . . . . . . . . 20 ⊢ (𝑙 = 𝑐 → {{𝑥, 𝑎}, {𝑥, 𝑙}} = {{𝑥, 𝑎}, {𝑥, 𝑐}})
27	26	sseq1d 3595	. . . . . . . . . . . . . . . . . . 19 ⊢ (𝑙 = 𝑐 → ({{𝑥, 𝑎}, {𝑥, 𝑙}} ⊆ ran 𝐸 ↔ {{𝑥, 𝑎}, {𝑥, 𝑐}} ⊆ ran 𝐸))
28	27	reubidv 3103	. . . . . . . . . . . . . . . . . 18 ⊢ (𝑙 = 𝑐 → (∃!𝑥 ∈ 𝑉 {{𝑥, 𝑎}, {𝑥, 𝑙}} ⊆ ran 𝐸 ↔ ∃!𝑥 ∈ 𝑉 {{𝑥, 𝑎}, {𝑥, 𝑐}} ⊆ ran 𝐸))
29	28	rspcv 3278	. . . . . . . . . . . . . . . . 17 ⊢ (𝑐 ∈ (𝑉 ∖ {𝑎}) → (∀𝑙 ∈ (𝑉 ∖ {𝑎})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑎}, {𝑥, 𝑙}} ⊆ ran 𝐸 → ∃!𝑥 ∈ 𝑉 {{𝑥, 𝑎}, {𝑥, 𝑐}} ⊆ ran 𝐸))
30	13, 24, 29	sylsyld 59	. . . . . . . . . . . . . . . 16 ⊢ ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → (∀𝑘 ∈ 𝑉 ∀𝑙 ∈ (𝑉 ∖ {𝑘})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑘}, {𝑥, 𝑙}} ⊆ ran 𝐸 → ∃!𝑥 ∈ 𝑉 {{𝑥, 𝑎}, {𝑥, 𝑐}} ⊆ ran 𝐸))
31		prcom 4211	. . . . . . . . . . . . . . . . . . . 20 ⊢ {𝑥, 𝑎} = {𝑎, 𝑥}
32	31	preq1i 4215	. . . . . . . . . . . . . . . . . . 19 ⊢ {{𝑥, 𝑎}, {𝑥, 𝑐}} = {{𝑎, 𝑥}, {𝑥, 𝑐}}
33	32	sseq1i 3592	. . . . . . . . . . . . . . . . . 18 ⊢ ({{𝑥, 𝑎}, {𝑥, 𝑐}} ⊆ ran 𝐸 ↔ {{𝑎, 𝑥}, {𝑥, 𝑐}} ⊆ ran 𝐸)
34	33	reubii 3105	. . . . . . . . . . . . . . . . 17 ⊢ (∃!𝑥 ∈ 𝑉 {{𝑥, 𝑎}, {𝑥, 𝑐}} ⊆ ran 𝐸 ↔ ∃!𝑥 ∈ 𝑉 {{𝑎, 𝑥}, {𝑥, 𝑐}} ⊆ ran 𝐸)
35		simpl 472	. . . . . . . . . . . . . . . . . . . . 21 ⊢ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) → ({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸))
36	35	ad2antrl 760	. . . . . . . . . . . . . . . . . . . 20 ⊢ ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → ({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸))
37		simpr 476	. . . . . . . . . . . . . . . . . . . . 21 ⊢ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) → ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸))
38	37	ad2antrl 760	. . . . . . . . . . . . . . . . . . . 20 ⊢ ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸))
39		simpr 476	. . . . . . . . . . . . . . . . . . . . . 22 ⊢ ((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) → 𝑏 ∈ 𝑉)
40	39	adantr 480	. . . . . . . . . . . . . . . . . . . . 21 ⊢ (((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) → 𝑏 ∈ 𝑉)
41	40	adantr 480	. . . . . . . . . . . . . . . . . . . 20 ⊢ ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → 𝑏 ∈ 𝑉)
42		simpr 476	. . . . . . . . . . . . . . . . . . . . . 22 ⊢ ((𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉) → 𝑑 ∈ 𝑉)
43	42	adantl 481	. . . . . . . . . . . . . . . . . . . . 21 ⊢ (((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) → 𝑑 ∈ 𝑉)
44	43	adantr 480	. . . . . . . . . . . . . . . . . . . 20 ⊢ ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → 𝑑 ∈ 𝑉)
45		simprr2 1103	. . . . . . . . . . . . . . . . . . . . 21 ⊢ (((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑))) → 𝑏 ≠ 𝑑)
46	45	adantl 481	. . . . . . . . . . . . . . . . . . . 20 ⊢ ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → 𝑏 ≠ 𝑑)
47		4cycl2vnunb 26544	. . . . . . . . . . . . . . . . . . . 20 ⊢ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸) ∧ (𝑏 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉 ∧ 𝑏 ≠ 𝑑)) → ¬ ∃!𝑥 ∈ 𝑉 {{𝑎, 𝑥}, {𝑥, 𝑐}} ⊆ ran 𝐸)
48	36, 38, 41, 44, 46, 47	syl113anc 1330	. . . . . . . . . . . . . . . . . . 19 ⊢ ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → ¬ ∃!𝑥 ∈ 𝑉 {{𝑎, 𝑥}, {𝑥, 𝑐}} ⊆ ran 𝐸)
49	48	pm2.21d 117	. . . . . . . . . . . . . . . . . 18 ⊢ ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → (∃!𝑥 ∈ 𝑉 {{𝑎, 𝑥}, {𝑥, 𝑐}} ⊆ ran 𝐸 → (#‘𝐹) ≠ 4))
50	49	com12 32	. . . . . . . . . . . . . . . . 17 ⊢ (∃!𝑥 ∈ 𝑉 {{𝑎, 𝑥}, {𝑥, 𝑐}} ⊆ ran 𝐸 → ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → (#‘𝐹) ≠ 4))
51	34, 50	sylbi 206	. . . . . . . . . . . . . . . 16 ⊢ (∃!𝑥 ∈ 𝑉 {{𝑥, 𝑎}, {𝑥, 𝑐}} ⊆ ran 𝐸 → ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → (#‘𝐹) ≠ 4))
52	30, 51	syl6 34	. . . . . . . . . . . . . . 15 ⊢ ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → (∀𝑘 ∈ 𝑉 ∀𝑙 ∈ (𝑉 ∖ {𝑘})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑘}, {𝑥, 𝑙}} ⊆ ran 𝐸 → ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → (#‘𝐹) ≠ 4)))
53	52	pm2.43b 53	. . . . . . . . . . . . . 14 ⊢ (∀𝑘 ∈ 𝑉 ∀𝑙 ∈ (𝑉 ∖ {𝑘})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑘}, {𝑥, 𝑙}} ⊆ ran 𝐸 → ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → (#‘𝐹) ≠ 4))
54	53	adantl 481	. . . . . . . . . . . . 13 ⊢ ((𝑉 USGrph 𝐸 ∧ ∀𝑘 ∈ 𝑉 ∀𝑙 ∈ (𝑉 ∖ {𝑘})∃!𝑥 ∈ 𝑉 {{𝑥, 𝑘}, {𝑥, 𝑙}} ⊆ ran 𝐸) → ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → (#‘𝐹) ≠ 4))
55	3, 54	syl 17	. . . . . . . . . . . 12 ⊢ (𝑉 FriendGrph 𝐸 → ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → (#‘𝐹) ≠ 4))
56	55	com12 32	. . . . . . . . . . 11 ⊢ ((((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) ∧ ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑)))) → (𝑉 FriendGrph 𝐸 → (#‘𝐹) ≠ 4))
57	56	ex 449	. . . . . . . . . 10 ⊢ (((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) ∧ (𝑐 ∈ 𝑉 ∧ 𝑑 ∈ 𝑉)) → (((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑))) → (𝑉 FriendGrph 𝐸 → (#‘𝐹) ≠ 4)))
58	57	rexlimdvva 3020	. . . . . . . . 9 ⊢ ((𝑎 ∈ 𝑉 ∧ 𝑏 ∈ 𝑉) → (∃𝑐 ∈ 𝑉 ∃𝑑 ∈ 𝑉 ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑))) → (𝑉 FriendGrph 𝐸 → (#‘𝐹) ≠ 4)))
59	58	rexlimivv 3018	. . . . . . . 8 ⊢ (∃𝑎 ∈ 𝑉 ∃𝑏 ∈ 𝑉 ∃𝑐 ∈ 𝑉 ∃𝑑 ∈ 𝑉 ((({𝑎, 𝑏} ∈ ran 𝐸 ∧ {𝑏, 𝑐} ∈ ran 𝐸) ∧ ({𝑐, 𝑑} ∈ ran 𝐸 ∧ {𝑑, 𝑎} ∈ ran 𝐸)) ∧ ((𝑎 ≠ 𝑏 ∧ 𝑎 ≠ 𝑐 ∧ 𝑎 ≠ 𝑑) ∧ (𝑏 ≠ 𝑐 ∧ 𝑏 ≠ 𝑑 ∧ 𝑐 ≠ 𝑑))) → (𝑉 FriendGrph 𝐸 → (#‘𝐹) ≠ 4))
60	2, 59	syl 17	. . . . . . 7 ⊢ ((𝑉 USGrph 𝐸 ∧ 𝐹(𝑉 Cycles 𝐸)𝑃 ∧ (#‘𝐹) = 4) → (𝑉 FriendGrph 𝐸 → (#‘𝐹) ≠ 4))
61	60	3exp 1256	. . . . . 6 ⊢ (𝑉 USGrph 𝐸 → (𝐹(𝑉 Cycles 𝐸)𝑃 → ((#‘𝐹) = 4 → (𝑉 FriendGrph 𝐸 → (#‘𝐹) ≠ 4))))
62	61	com34 89	. . . . 5 ⊢ (𝑉 USGrph 𝐸 → (𝐹(𝑉 Cycles 𝐸)𝑃 → (𝑉 FriendGrph 𝐸 → ((#‘𝐹) = 4 → (#‘𝐹) ≠ 4))))
63	62	com23 84	. . . 4 ⊢ (𝑉 USGrph 𝐸 → (𝑉 FriendGrph 𝐸 → (𝐹(𝑉 Cycles 𝐸)𝑃 → ((#‘𝐹) = 4 → (#‘𝐹) ≠ 4))))
64	1, 63	mpcom 37	. . 3 ⊢ (𝑉 FriendGrph 𝐸 → (𝐹(𝑉 Cycles 𝐸)𝑃 → ((#‘𝐹) = 4 → (#‘𝐹) ≠ 4)))
65	64	imp 444	. 2 ⊢ ((𝑉 FriendGrph 𝐸 ∧ 𝐹(𝑉 Cycles 𝐸)𝑃) → ((#‘𝐹) = 4 → (#‘𝐹) ≠ 4))
66		df-ne 2782	. . 3 ⊢ ((#‘𝐹) ≠ 4 ↔ ¬ (#‘𝐹) = 4)
67	66	biimpri 217	. 2 ⊢ (¬ (#‘𝐹) = 4 → (#‘𝐹) ≠ 4)
68	65, 67	pm2.61d1 170	1 ⊢ ((𝑉 FriendGrph 𝐸 ∧ 𝐹(𝑉 Cycles 𝐸)𝑃) → (#‘𝐹) ≠ 4)

Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 383   ∧ w3a 1031   = wceq 1475   ∈ wcel 1977   ≠ wne 2780  ∀wral 2896  ∃wrex 2897  ∃!wreu 2898   ∖ cdif 3537   ⊆ wss 3540  {csn 4125  {cpr 4127   class class class wbr 4583  ran crn 5039  ‘cfv 5804  (class class class)co 6549  4c4 10949  #chash 12979   USGrph cusg 25859   Cycles ccycl 26035   FriendGrph cfrgra 26515

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1713  ax-4 1728  ax-5 1827  ax-6 1875  ax-7 1922  ax-8 1979  ax-9 1986  ax-10 2006  ax-11 2021  ax-12 2034  ax-13 2234  ax-ext 2590  ax-rep 4699  ax-sep 4709  ax-nul 4717  ax-pow 4769  ax-pr 4833  ax-un 6847  ax-cnex 9871  ax-resscn 9872  ax-1cn 9873  ax-icn 9874  ax-addcl 9875  ax-addrcl 9876  ax-mulcl 9877  ax-mulrcl 9878  ax-mulcom 9879  ax-addass 9880  ax-mulass 9881  ax-distr 9882  ax-i2m1 9883  ax-1ne0 9884  ax-1rid 9885  ax-rnegex 9886  ax-rrecex 9887  ax-cnre 9888  ax-pre-lttri 9889  ax-pre-lttrn 9890  ax-pre-ltadd 9891  ax-pre-mulgt0 9892

This theorem depends on definitions:  df-bi 196  df-or 384  df-an 385  df-3or 1032  df-3an 1033  df-tru 1478  df-ex 1696  df-nf 1701  df-sb 1868  df-eu 2462  df-mo 2463  df-clab 2597  df-cleq 2603  df-clel 2606  df-nfc 2740  df-ne 2782  df-nel 2783  df-ral 2901  df-rex 2902  df-reu 2903  df-rmo 2904  df-rab 2905  df-v 3175  df-sbc 3403  df-csb 3500  df-dif 3543  df-un 3545  df-in 3547  df-ss 3554  df-pss 3556  df-nul 3875  df-if 4037  df-pw 4110  df-sn 4126  df-pr 4128  df-tp 4130  df-op 4132  df-uni 4373  df-int 4411  df-iun 4457  df-br 4584  df-opab 4644  df-mpt 4645  df-tr 4681  df-eprel 4949  df-id 4953  df-po 4959  df-so 4960  df-fr 4997  df-we 4999  df-xp 5044  df-rel 5045  df-cnv 5046  df-co 5047  df-dm 5048  df-rn 5049  df-res 5050  df-ima 5051  df-pred 5597  df-ord 5643  df-on 5644  df-lim 5645  df-suc 5646  df-iota 5768  df-fun 5806  df-fn 5807  df-f 5808  df-f1 5809  df-fo 5810  df-f1o 5811  df-fv 5812  df-riota 6511  df-ov 6552  df-oprab 6553  df-mpt2 6554  df-om 6958  df-1st 7059  df-2nd 7060  df-wrecs 7294  df-recs 7355  df-rdg 7393  df-1o 7447  df-oadd 7451  df-er 7629  df-map 7746  df-pm 7747  df-en 7842  df-dom 7843  df-sdom 7844  df-fin 7845  df-card 8648  df-cda 8873  df-pnf 9955  df-mnf 9956  df-xr 9957  df-ltxr 9958  df-le 9959  df-sub 10147  df-neg 10148  df-nn 10898  df-2 10956  df-3 10957  df-4 10958  df-n0 11170  df-z 11255  df-uz 11564  df-fz 12198  df-fzo 12335  df-hash 12980  df-word 13154  df-usgra 25862  df-wlk 26036  df-trail 26037  df-pth 26038  df-cycl 26041  df-frgra 26516

This theorem is referenced by: (None)