vtxdgfifival - Intuitionistic Logic Explorer

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Theorem vtxdgfifival 16737

Description: The degree of a vertex for graphs with finite vertex and edge sets. (Contributed by Jim Kingdon, 10-Feb-2026.)

**Hypotheses**
Ref	Expression
vtxdgval.v	⊢ 𝑉 = (Vtx‘𝐺)
vtxdgval.i	⊢ 𝐼 = (iEdg‘𝐺)
vtxdgval.a	⊢ 𝐴 = dom 𝐼
vtxdgfifival.a	⊢ (𝜑 → 𝐴 ∈ Fin)
vtxdgfifival.v	⊢ (𝜑 → 𝑉 ∈ Fin)
vtxdgfifival.u	⊢ (𝜑 → 𝑈 ∈ 𝑉)
vtxdgfifival.g	⊢ (𝜑 → 𝐺 ∈ UPGraph)

**Assertion**
Ref	Expression
vtxdgfifival	⊢ (𝜑 → ((VtxDeg‘𝐺)‘𝑈) = ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)}) + (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}})))

Distinct variable groups: 𝑥,𝐴 𝑥,𝐺 𝑥,𝐼 𝑥,𝑈 𝑥,𝑉 Allowed substitution hint: 𝜑(𝑥)

Proof of Theorem vtxdgfifival Dummy variable 𝑢 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		vtxdgfifival.u	. . 3 ⊢ (𝜑 → 𝑈 ∈ 𝑉)
2		vtxdgval.v	. . . . . 6 ⊢ 𝑉 = (Vtx‘𝐺)
3	2	1vgrex 16466	. . . . 5 ⊢ (𝑈 ∈ 𝑉 → 𝐺 ∈ V)
4		vtxdgval.i	. . . . . 6 ⊢ 𝐼 = (iEdg‘𝐺)
5		vtxdgval.a	. . . . . 6 ⊢ 𝐴 = dom 𝐼
6	2, 4, 5	vtxdgfval 16734	. . . . 5 ⊢ (𝐺 ∈ V → (VtxDeg‘𝐺) = (𝑢 ∈ 𝑉 ↦ ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑢 ∈ (𝐼‘𝑥)}) +_e (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑢}}))))
7	3, 6	syl 14	. . . 4 ⊢ (𝑈 ∈ 𝑉 → (VtxDeg‘𝐺) = (𝑢 ∈ 𝑉 ↦ ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑢 ∈ (𝐼‘𝑥)}) +_e (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑢}}))))
8	7	fveq1d 5700	. . 3 ⊢ (𝑈 ∈ 𝑉 → ((VtxDeg‘𝐺)‘𝑈) = ((𝑢 ∈ 𝑉 ↦ ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑢 ∈ (𝐼‘𝑥)}) +_e (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑢}})))‘𝑈))
9	1, 8	syl 14	. 2 ⊢ (𝜑 → ((VtxDeg‘𝐺)‘𝑈) = ((𝑢 ∈ 𝑉 ↦ ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑢 ∈ (𝐼‘𝑥)}) +_e (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑢}})))‘𝑈))
10		eqid 2238	. . 3 ⊢ (𝑢 ∈ 𝑉 ↦ ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑢 ∈ (𝐼‘𝑥)}) +_e (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑢}}))) = (𝑢 ∈ 𝑉 ↦ ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑢 ∈ (𝐼‘𝑥)}) +_e (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑢}})))
11		eleq1 2301	. . . . . 6 ⊢ (𝑢 = 𝑈 → (𝑢 ∈ (𝐼‘𝑥) ↔ 𝑈 ∈ (𝐼‘𝑥)))
12	11	rabbidv 2810	. . . . 5 ⊢ (𝑢 = 𝑈 → {𝑥 ∈ 𝐴 ∣ 𝑢 ∈ (𝐼‘𝑥)} = {𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)})
13	12	fveq2d 5702	. . . 4 ⊢ (𝑢 = 𝑈 → (♯‘{𝑥 ∈ 𝐴 ∣ 𝑢 ∈ (𝐼‘𝑥)}) = (♯‘{𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)}))
14		sneq 3720	. . . . . . 7 ⊢ (𝑢 = 𝑈 → {𝑢} = {𝑈})
15	14	eqeq2d 2250	. . . . . 6 ⊢ (𝑢 = 𝑈 → ((𝐼‘𝑥) = {𝑢} ↔ (𝐼‘𝑥) = {𝑈}))
16	15	rabbidv 2810	. . . . 5 ⊢ (𝑢 = 𝑈 → {𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑢}} = {𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}})
17	16	fveq2d 5702	. . . 4 ⊢ (𝑢 = 𝑈 → (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑢}}) = (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}}))
18	13, 17	oveq12d 6106	. . 3 ⊢ (𝑢 = 𝑈 → ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑢 ∈ (𝐼‘𝑥)}) +_e (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑢}})) = ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)}) +_e (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}})))
19		vtxdgfifival.a	. . . . . . . 8 ⊢ (𝜑 → 𝐴 ∈ Fin)
20		vtxdgfifival.v	. . . . . . . 8 ⊢ (𝜑 → 𝑉 ∈ Fin)
21		vtxdgfifival.g	. . . . . . . 8 ⊢ (𝜑 → 𝐺 ∈ UPGraph)
22	2, 4, 5, 19, 20, 1, 21	vtxedgfi 16735	. . . . . . 7 ⊢ (𝜑 → {𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)} ∈ Fin)
23		hashcl 11242	. . . . . . 7 ⊢ ({𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)} ∈ Fin → (♯‘{𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)}) ∈ ℕ₀)
24	22, 23	syl 14	. . . . . 6 ⊢ (𝜑 → (♯‘{𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)}) ∈ ℕ₀)
25	24	nn0red 9632	. . . . 5 ⊢ (𝜑 → (♯‘{𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)}) ∈ ℝ)
26	25	rexrd 8381	. . . 4 ⊢ (𝜑 → (♯‘{𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)}) ∈ ℝ^*)
27	2, 4, 5, 19, 20, 1, 21	vtxlpfi 16736	. . . . . . 7 ⊢ (𝜑 → {𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}} ∈ Fin)
28		hashcl 11242	. . . . . . 7 ⊢ ({𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}} ∈ Fin → (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}}) ∈ ℕ₀)
29	27, 28	syl 14	. . . . . 6 ⊢ (𝜑 → (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}}) ∈ ℕ₀)
30	29	nn0red 9632	. . . . 5 ⊢ (𝜑 → (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}}) ∈ ℝ)
31	30	rexrd 8381	. . . 4 ⊢ (𝜑 → (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}}) ∈ ℝ^*)
32	26, 31	xaddcld 10303	. . 3 ⊢ (𝜑 → ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)}) +_e (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}})) ∈ ℝ^*)
33	10, 18, 1, 32	fvmptd3 5802	. 2 ⊢ (𝜑 → ((𝑢 ∈ 𝑉 ↦ ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑢 ∈ (𝐼‘𝑥)}) +_e (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑢}})))‘𝑈) = ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)}) +_e (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}})))
34	25, 30	rexaddd 10273	. 2 ⊢ (𝜑 → ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)}) +_e (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}})) = ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)}) + (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}})))
35	9, 33, 34	3eqtrd 2275	1 ⊢ (𝜑 → ((VtxDeg‘𝐺)‘𝑈) = ((♯‘{𝑥 ∈ 𝐴 ∣ 𝑈 ∈ (𝐼‘𝑥)}) + (♯‘{𝑥 ∈ 𝐴 ∣ (𝐼‘𝑥) = {𝑈}})))

Colors of variables: wff set class

This proof depends on syntax axioms: → wi 4 = wceq 1402 ∈ wcel 2209 {crab 2532 Vcvv 2821 {csn 3709 ↦ cmpt 4193 dom cdm 4776 ‘cfv 5380 (class class class)co 6088 Fincfn 7026 + caddc 8188 ℝ^*cxr 8365 ℕ₀cn0 9574 +_e cxad 10189 ♯chash 11236 Vtxcvtx 16458 iEdgciedg 16459 UPGraphcupgr 16537 VtxDegcvtxdg 16732

This proof depends on axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 106 ax-ia2 107 ax-ia3 108 ax-in1 623 ax-in2 624 ax-io 721 ax-5 1500 ax-7 1501 ax-gen 1502 ax-ie1 1546 ax-ie2 1547 ax-8 1557 ax-10 1558 ax-11 1559 ax-i12 1560 ax-bndl 1562 ax-4 1563 ax-17 1579 ax-i9 1583 ax-ial 1587 ax-i5r 1588 ax-14 2212 ax-ext 2220 ax-coll 4248 ax-sep 4251 ax-nul 4261 ax-pow 4313 ax-pr 4348 ax-un 4580 ax-setind 4686 ax-iinf 4737 ax-cnex 8276 ax-resscn 8277 ax-1cn 8278 ax-1re 8279 ax-icn 8280 ax-addcl 8281 ax-addrcl 8282 ax-mulcl 8283 ax-addcom 8285 ax-mulcom 8286 ax-addass 8287 ax-mulass 8288 ax-distr 8289 ax-i2m1 8290 ax-0lt1 8291 ax-1rid 8292 ax-0id 8293 ax-rnegex 8294 ax-cnre 8296 ax-pre-ltirr 8297 ax-pre-ltwlin 8298 ax-pre-lttrn 8299 ax-pre-ltadd 8301

This proof depends on definitions: df-bi 117 df-dc 847 df-3or 1010 df-3an 1011 df-tru 1405 df-fal 1408 df-nf 1514 df-sb 1816 df-eu 2089 df-mo 2090 df-clab 2225 df-cleq 2231 df-clel 2234 df-nfc 2381 df-ne 2421 df-nel 2516 df-ral 2533 df-rex 2534 df-reu 2535 df-rab 2537 df-v 2823 df-sbc 3052 df-csb 3148 df-dif 3222 df-un 3224 df-in 3226 df-ss 3233 df-nul 3521 df-if 3639 df-pw 3690 df-sn 3715 df-pr 3716 df-op 3718 df-uni 3936 df-int 3971 df-iun 4014 df-br 4132 df-opab 4194 df-mpt 4195 df-tr 4232 df-id 4440 df-iord 4513 df-on 4515 df-ilim 4516 df-suc 4518 df-iom 4740 df-xp 4782 df-rel 4783 df-cnv 4784 df-co 4785 df-dm 4786 df-rn 4787 df-res 4788 df-ima 4789 df-iota 5340 df-fun 5382 df-fn 5383 df-f 5384 df-f1 5385 df-fo 5386 df-f1o 5387 df-fv 5388 df-riota 6041 df-ov 6091 df-oprab 6092 df-mpo 6093 df-1st 6378 df-2nd 6379 df-recs 6580 df-frec 6666 df-1o 6691 df-2o 6692 df-er 6811 df-en 7027 df-dom 7028 df-fin 7029 df-pnf 8368 df-mnf 8369 df-xr 8370 df-ltxr 8371 df-le 8372 df-sub 8506 df-neg 8507 df-inn 9314 df-2 9372 df-3 9373 df-4 9374 df-5 9375 df-6 9376 df-7 9377 df-8 9378 df-9 9379 df-n0 9575 df-z 9656 df-dec 9789 df-uz 9938 df-xadd 10192 df-ihash 11237 df-ndx 13413 df-slot 13414 df-base 13416 df-edgf 16451 df-vtx 16460 df-iedg 16461 df-upgren 16539 df-vtxdg 16733

This theorem is used by: vtxdgfi0e 16741 vtxdfifiun 16743 vtxdumgrfival 16744 vtxd0nedgbfi 16745 vtxduspgrfvedgfi 16747

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