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Theorem vtxd0nedgbfi 16420

Description: A vertex has degree 0 iff there is no edge incident with the vertex. (Contributed by AV, 24-Dec-2020.) (Revised by AV, 22-Mar-2021.)

**Hypotheses**
Ref	Expression
vtxd0nedgb.v	⊢ 𝑉 = (Vtx‘𝐺)
vtxd0nedgb.i	⊢ 𝐼 = (iEdg‘𝐺)
vtxd0nedgb.d	⊢ 𝐷 = (VtxDeg‘𝐺)
vtxd0nedgbfi.i	⊢ (𝜑 → dom 𝐼 ∈ Fin)
vtxd0nedgbfi.v	⊢ (𝜑 → 𝑉 ∈ Fin)
vtxd0nedgbfi.u	⊢ (𝜑 → 𝑈 ∈ 𝑉)
vtxd0nedgbfi.g	⊢ (𝜑 → 𝐺 ∈ UPGraph)

**Assertion**
Ref	Expression
vtxd0nedgbfi	⊢ (𝜑 → ((𝐷‘𝑈) = 0 ↔ ¬ ∃𝑖 ∈ dom 𝐼 𝑈 ∈ (𝐼‘𝑖)))

Distinct variable groups: 𝑖,𝐺 𝑖,𝐼 𝑈,𝑖 𝑖,𝑉 Allowed substitution hints: 𝜑(𝑖) 𝐷(𝑖)

**Proof of Theorem vtxd0nedgbfi**
Step	Hyp	Ref	Expression
1		vtxd0nedgb.d	. . . . 5 ⊢ 𝐷 = (VtxDeg‘𝐺)
2	1	fveq1i 5676	. . . 4 ⊢ (𝐷‘𝑈) = ((VtxDeg‘𝐺)‘𝑈)
3		vtxd0nedgb.v	. . . . 5 ⊢ 𝑉 = (Vtx‘𝐺)
4		vtxd0nedgb.i	. . . . 5 ⊢ 𝐼 = (iEdg‘𝐺)
5		eqid 2234	. . . . 5 ⊢ dom 𝐼 = dom 𝐼
6		vtxd0nedgbfi.i	. . . . 5 ⊢ (𝜑 → dom 𝐼 ∈ Fin)
7		vtxd0nedgbfi.v	. . . . 5 ⊢ (𝜑 → 𝑉 ∈ Fin)
8		vtxd0nedgbfi.u	. . . . 5 ⊢ (𝜑 → 𝑈 ∈ 𝑉)
9		vtxd0nedgbfi.g	. . . . 5 ⊢ (𝜑 → 𝐺 ∈ UPGraph)
10	3, 4, 5, 6, 7, 8, 9	vtxdgfifival 16412	. . . 4 ⊢ (𝜑 → ((VtxDeg‘𝐺)‘𝑈) = ((♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) + (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}})))
11	2, 10	eqtrid 2279	. . 3 ⊢ (𝜑 → (𝐷‘𝑈) = ((♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) + (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}})))
12	11	eqeq1d 2243	. 2 ⊢ (𝜑 → ((𝐷‘𝑈) = 0 ↔ ((♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) + (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}})) = 0))
13	3, 4, 5, 6, 7, 8, 9	vtxedgfi 16410	. . . . 5 ⊢ (𝜑 → {𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)} ∈ Fin)
14		hashcl 11169	. . . . 5 ⊢ ({𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)} ∈ Fin → (♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) ∈ ℕ₀)
15	13, 14	syl 14	. . . 4 ⊢ (𝜑 → (♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) ∈ ℕ₀)
16	15	nn0red 9571	. . 3 ⊢ (𝜑 → (♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) ∈ ℝ)
17	15	nn0ge0d 9573	. . 3 ⊢ (𝜑 → 0 ≤ (♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}))
18	3, 4, 5, 6, 7, 8, 9	vtxlpfi 16411	. . . . 5 ⊢ (𝜑 → {𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}} ∈ Fin)
19		hashcl 11169	. . . . 5 ⊢ ({𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}} ∈ Fin → (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}}) ∈ ℕ₀)
20	18, 19	syl 14	. . . 4 ⊢ (𝜑 → (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}}) ∈ ℕ₀)
21	20	nn0red 9571	. . 3 ⊢ (𝜑 → (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}}) ∈ ℝ)
22	20	nn0ge0d 9573	. . 3 ⊢ (𝜑 → 0 ≤ (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}}))
23		add20 8765	. . 3 ⊢ ((((♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) ∈ ℝ ∧ 0 ≤ (♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)})) ∧ ((♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}}) ∈ ℝ ∧ 0 ≤ (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}}))) → (((♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) + (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}})) = 0 ↔ ((♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) = 0 ∧ (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}}) = 0)))
24	16, 17, 21, 22, 23	syl22anc 1275	. 2 ⊢ (𝜑 → (((♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) + (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}})) = 0 ↔ ((♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) = 0 ∧ (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}}) = 0)))
25		fihasheq0 11181	. . . . . 6 ⊢ ({𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)} ∈ Fin → ((♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) = 0 ↔ {𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)} = ∅))
26	13, 25	syl 14	. . . . 5 ⊢ (𝜑 → ((♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) = 0 ↔ {𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)} = ∅))
27		fihasheq0 11181	. . . . . 6 ⊢ ({𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}} ∈ Fin → ((♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}}) = 0 ↔ {𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}} = ∅))
28	18, 27	syl 14	. . . . 5 ⊢ (𝜑 → ((♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}}) = 0 ↔ {𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}} = ∅))
29	26, 28	anbi12d 473	. . . 4 ⊢ (𝜑 → (((♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) = 0 ∧ (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}}) = 0) ↔ ({𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)} = ∅ ∧ {𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}} = ∅)))
30		rabeq0 3542	. . . . . 6 ⊢ ({𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)} = ∅ ↔ ∀𝑖 ∈ dom 𝐼 ¬ 𝑈 ∈ (𝐼‘𝑖))
31		rabeq0 3542	. . . . . 6 ⊢ ({𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}} = ∅ ↔ ∀𝑖 ∈ dom 𝐼 ¬ (𝐼‘𝑖) = {𝑈})
32	30, 31	anbi12i 460	. . . . 5 ⊢ (({𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)} = ∅ ∧ {𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}} = ∅) ↔ (∀𝑖 ∈ dom 𝐼 ¬ 𝑈 ∈ (𝐼‘𝑖) ∧ ∀𝑖 ∈ dom 𝐼 ¬ (𝐼‘𝑖) = {𝑈}))
33	32	a1i 9	. . . 4 ⊢ (𝜑 → (({𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)} = ∅ ∧ {𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}} = ∅) ↔ (∀𝑖 ∈ dom 𝐼 ¬ 𝑈 ∈ (𝐼‘𝑖) ∧ ∀𝑖 ∈ dom 𝐼 ¬ (𝐼‘𝑖) = {𝑈})))
34		ioran 760	. . . . . . 7 ⊢ (¬ (𝑈 ∈ (𝐼‘𝑖) ∨ (𝐼‘𝑖) = {𝑈}) ↔ (¬ 𝑈 ∈ (𝐼‘𝑖) ∧ ¬ (𝐼‘𝑖) = {𝑈}))
35	34	ralbii 2550	. . . . . 6 ⊢ (∀𝑖 ∈ dom 𝐼 ¬ (𝑈 ∈ (𝐼‘𝑖) ∨ (𝐼‘𝑖) = {𝑈}) ↔ ∀𝑖 ∈ dom 𝐼(¬ 𝑈 ∈ (𝐼‘𝑖) ∧ ¬ (𝐼‘𝑖) = {𝑈}))
36		ralnex 2532	. . . . . 6 ⊢ (∀𝑖 ∈ dom 𝐼 ¬ (𝑈 ∈ (𝐼‘𝑖) ∨ (𝐼‘𝑖) = {𝑈}) ↔ ¬ ∃𝑖 ∈ dom 𝐼(𝑈 ∈ (𝐼‘𝑖) ∨ (𝐼‘𝑖) = {𝑈}))
37		r19.26 2671	. . . . . 6 ⊢ (∀𝑖 ∈ dom 𝐼(¬ 𝑈 ∈ (𝐼‘𝑖) ∧ ¬ (𝐼‘𝑖) = {𝑈}) ↔ (∀𝑖 ∈ dom 𝐼 ¬ 𝑈 ∈ (𝐼‘𝑖) ∧ ∀𝑖 ∈ dom 𝐼 ¬ (𝐼‘𝑖) = {𝑈}))
38	35, 36, 37	3bitr3ri 211	. . . . 5 ⊢ ((∀𝑖 ∈ dom 𝐼 ¬ 𝑈 ∈ (𝐼‘𝑖) ∧ ∀𝑖 ∈ dom 𝐼 ¬ (𝐼‘𝑖) = {𝑈}) ↔ ¬ ∃𝑖 ∈ dom 𝐼(𝑈 ∈ (𝐼‘𝑖) ∨ (𝐼‘𝑖) = {𝑈}))
39	38	a1i 9	. . . 4 ⊢ (𝜑 → ((∀𝑖 ∈ dom 𝐼 ¬ 𝑈 ∈ (𝐼‘𝑖) ∧ ∀𝑖 ∈ dom 𝐼 ¬ (𝐼‘𝑖) = {𝑈}) ↔ ¬ ∃𝑖 ∈ dom 𝐼(𝑈 ∈ (𝐼‘𝑖) ∨ (𝐼‘𝑖) = {𝑈})))
40	29, 33, 39	3bitrd 214	. . 3 ⊢ (𝜑 → (((♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) = 0 ∧ (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}}) = 0) ↔ ¬ ∃𝑖 ∈ dom 𝐼(𝑈 ∈ (𝐼‘𝑖) ∨ (𝐼‘𝑖) = {𝑈})))
41		orcom 736	. . . . . . 7 ⊢ ((𝑈 ∈ (𝐼‘𝑖) ∨ (𝐼‘𝑖) = {𝑈}) ↔ ((𝐼‘𝑖) = {𝑈} ∨ 𝑈 ∈ (𝐼‘𝑖)))
42		snidg 3723	. . . . . . . . 9 ⊢ (𝑈 ∈ 𝑉 → 𝑈 ∈ {𝑈})
43		eleq2 2298	. . . . . . . . 9 ⊢ ((𝐼‘𝑖) = {𝑈} → (𝑈 ∈ (𝐼‘𝑖) ↔ 𝑈 ∈ {𝑈}))
44	42, 43	syl5ibrcom 157	. . . . . . . 8 ⊢ (𝑈 ∈ 𝑉 → ((𝐼‘𝑖) = {𝑈} → 𝑈 ∈ (𝐼‘𝑖)))
45		pm4.72 835	. . . . . . . 8 ⊢ (((𝐼‘𝑖) = {𝑈} → 𝑈 ∈ (𝐼‘𝑖)) ↔ (𝑈 ∈ (𝐼‘𝑖) ↔ ((𝐼‘𝑖) = {𝑈} ∨ 𝑈 ∈ (𝐼‘𝑖))))
46	44, 45	sylib 122	. . . . . . 7 ⊢ (𝑈 ∈ 𝑉 → (𝑈 ∈ (𝐼‘𝑖) ↔ ((𝐼‘𝑖) = {𝑈} ∨ 𝑈 ∈ (𝐼‘𝑖))))
47	41, 46	bitr4id 199	. . . . . 6 ⊢ (𝑈 ∈ 𝑉 → ((𝑈 ∈ (𝐼‘𝑖) ∨ (𝐼‘𝑖) = {𝑈}) ↔ 𝑈 ∈ (𝐼‘𝑖)))
48	47	rexbidv 2545	. . . . 5 ⊢ (𝑈 ∈ 𝑉 → (∃𝑖 ∈ dom 𝐼(𝑈 ∈ (𝐼‘𝑖) ∨ (𝐼‘𝑖) = {𝑈}) ↔ ∃𝑖 ∈ dom 𝐼 𝑈 ∈ (𝐼‘𝑖)))
49	48	notbid 673	. . . 4 ⊢ (𝑈 ∈ 𝑉 → (¬ ∃𝑖 ∈ dom 𝐼(𝑈 ∈ (𝐼‘𝑖) ∨ (𝐼‘𝑖) = {𝑈}) ↔ ¬ ∃𝑖 ∈ dom 𝐼 𝑈 ∈ (𝐼‘𝑖)))
50	8, 49	syl 14	. . 3 ⊢ (𝜑 → (¬ ∃𝑖 ∈ dom 𝐼(𝑈 ∈ (𝐼‘𝑖) ∨ (𝐼‘𝑖) = {𝑈}) ↔ ¬ ∃𝑖 ∈ dom 𝐼 𝑈 ∈ (𝐼‘𝑖)))
51	40, 50	bitrd 188	. 2 ⊢ (𝜑 → (((♯‘{𝑖 ∈ dom 𝐼 ∣ 𝑈 ∈ (𝐼‘𝑖)}) = 0 ∧ (♯‘{𝑖 ∈ dom 𝐼 ∣ (𝐼‘𝑖) = {𝑈}}) = 0) ↔ ¬ ∃𝑖 ∈ dom 𝐼 𝑈 ∈ (𝐼‘𝑖)))
52	12, 24, 51	3bitrd 214	1 ⊢ (𝜑 → ((𝐷‘𝑈) = 0 ↔ ¬ ∃𝑖 ∈ dom 𝐼 𝑈 ∈ (𝐼‘𝑖)))

Colors of variables: wff set class

Syntax hints: ¬ wn 3 → wi 4 ∧ wa 104 ↔ wb 105 ∨ wo 716 = wceq 1398 ∈ wcel 2205 ∀wral 2522 ∃wrex 2523 {crab 2526 ∅c0 3512 {csn 3694 class class class wbr 4114 dom cdm 4754 ‘cfv 5357 (class class class)co 6058 Fincfn 6988 ℝcr 8142 0cc0 8143 + caddc 8146 ≤ cle 8325 ℕ₀cn0 9513 ♯chash 11163 Vtxcvtx 16133 iEdgciedg 16134 UPGraphcupgr 16212 VtxDegcvtxdg 16407

This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 106 ax-ia2 107 ax-ia3 108 ax-in1 619 ax-in2 620 ax-io 717 ax-5 1496 ax-7 1497 ax-gen 1498 ax-ie1 1542 ax-ie2 1543 ax-8 1553 ax-10 1554 ax-11 1555 ax-i12 1556 ax-bndl 1558 ax-4 1559 ax-17 1575 ax-i9 1579 ax-ial 1583 ax-i5r 1584 ax-13 2207 ax-14 2208 ax-ext 2216 ax-coll 4230 ax-sep 4233 ax-nul 4241 ax-pow 4292 ax-pr 4327 ax-un 4559 ax-setind 4664 ax-iinf 4715 ax-cnex 8234 ax-resscn 8235 ax-1cn 8236 ax-1re 8237 ax-icn 8238 ax-addcl 8239 ax-addrcl 8240 ax-mulcl 8241 ax-addcom 8243 ax-mulcom 8244 ax-addass 8245 ax-mulass 8246 ax-distr 8247 ax-i2m1 8248 ax-0lt1 8249 ax-1rid 8250 ax-0id 8251 ax-rnegex 8252 ax-cnre 8254 ax-pre-ltirr 8255 ax-pre-ltwlin 8256 ax-pre-lttrn 8257 ax-pre-apti 8258 ax-pre-ltadd 8259

This theorem depends on definitions: df-bi 117 df-dc 843 df-3or 1006 df-3an 1007 df-tru 1401 df-fal 1404 df-nf 1510 df-sb 1812 df-eu 2085 df-mo 2086 df-clab 2221 df-cleq 2227 df-clel 2230 df-nfc 2375 df-ne 2415 df-nel 2510 df-ral 2527 df-rex 2528 df-reu 2529 df-rab 2531 df-v 2817 df-sbc 3046 df-csb 3142 df-dif 3216 df-un 3218 df-in 3220 df-ss 3227 df-nul 3513 df-if 3625 df-pw 3676 df-sn 3700 df-pr 3701 df-op 3703 df-uni 3920 df-int 3955 df-iun 3998 df-br 4115 df-opab 4177 df-mpt 4178 df-tr 4214 df-id 4419 df-iord 4492 df-on 4494 df-ilim 4495 df-suc 4497 df-iom 4718 df-xp 4760 df-rel 4761 df-cnv 4762 df-co 4763 df-dm 4764 df-rn 4765 df-res 4766 df-ima 4767 df-iota 5317 df-fun 5359 df-fn 5360 df-f 5361 df-f1 5362 df-fo 5363 df-f1o 5364 df-fv 5365 df-riota 6011 df-ov 6061 df-oprab 6062 df-mpo 6063 df-1st 6347 df-2nd 6348 df-recs 6549 df-frec 6635 df-1o 6660 df-2o 6661 df-er 6780 df-en 6989 df-dom 6990 df-fin 6991 df-pnf 8326 df-mnf 8327 df-xr 8328 df-ltxr 8329 df-le 8330 df-sub 8462 df-neg 8463 df-inn 9255 df-2 9313 df-3 9314 df-4 9315 df-5 9316 df-6 9317 df-7 9318 df-8 9319 df-9 9320 df-n0 9514 df-z 9595 df-dec 9728 df-uz 9872 df-xadd 10125 df-fz 10362 df-ihash 11164 df-ndx 13299 df-slot 13300 df-base 13302 df-edgf 16126 df-vtx 16135 df-iedg 16136 df-upgren 16214 df-vtxdg 16408

This theorem is referenced by: 1loopgrvd0fi 16427 1hevtxdg0fi 16428

W3C validator