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Mirrors > Home > MPE Home > Th. List > fusgrn0degnn0 | Structured version Visualization version GIF version |
Description: In a nonempty, finite graph there is a vertex having a nonnegative integer as degree. (Contributed by Alexander van der Vekens, 6-Sep-2018.) (Revised by AV, 1-Apr-2021.) |
Ref | Expression |
---|---|
fusgrn0degnn0.v | ⊢ 𝑉 = (Vtx‘𝐺) |
Ref | Expression |
---|---|
fusgrn0degnn0 | ⊢ ((𝐺 ∈ FinUSGraph ∧ 𝑉 ≠ ∅) → ∃𝑣 ∈ 𝑉 ∃𝑛 ∈ ℕ0 ((VtxDeg‘𝐺)‘𝑣) = 𝑛) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | n0 4190 | . . 3 ⊢ (𝑉 ≠ ∅ ↔ ∃𝑘 𝑘 ∈ 𝑉) | |
2 | fusgrn0degnn0.v | . . . . . 6 ⊢ 𝑉 = (Vtx‘𝐺) | |
3 | 2 | vtxdgfusgr 26977 | . . . . 5 ⊢ (𝐺 ∈ FinUSGraph → ∀𝑢 ∈ 𝑉 ((VtxDeg‘𝐺)‘𝑢) ∈ ℕ0) |
4 | fveq2 6493 | . . . . . . . 8 ⊢ (𝑢 = 𝑘 → ((VtxDeg‘𝐺)‘𝑢) = ((VtxDeg‘𝐺)‘𝑘)) | |
5 | 4 | eleq1d 2844 | . . . . . . 7 ⊢ (𝑢 = 𝑘 → (((VtxDeg‘𝐺)‘𝑢) ∈ ℕ0 ↔ ((VtxDeg‘𝐺)‘𝑘) ∈ ℕ0)) |
6 | 5 | rspcv 3525 | . . . . . 6 ⊢ (𝑘 ∈ 𝑉 → (∀𝑢 ∈ 𝑉 ((VtxDeg‘𝐺)‘𝑢) ∈ ℕ0 → ((VtxDeg‘𝐺)‘𝑘) ∈ ℕ0)) |
7 | risset 3207 | . . . . . . . 8 ⊢ (((VtxDeg‘𝐺)‘𝑘) ∈ ℕ0 ↔ ∃𝑛 ∈ ℕ0 𝑛 = ((VtxDeg‘𝐺)‘𝑘)) | |
8 | fveqeq2 6502 | . . . . . . . . . . . 12 ⊢ (𝑣 = 𝑘 → (((VtxDeg‘𝐺)‘𝑣) = 𝑛 ↔ ((VtxDeg‘𝐺)‘𝑘) = 𝑛)) | |
9 | eqcom 2779 | . . . . . . . . . . . 12 ⊢ (((VtxDeg‘𝐺)‘𝑘) = 𝑛 ↔ 𝑛 = ((VtxDeg‘𝐺)‘𝑘)) | |
10 | 8, 9 | syl6bb 279 | . . . . . . . . . . 11 ⊢ (𝑣 = 𝑘 → (((VtxDeg‘𝐺)‘𝑣) = 𝑛 ↔ 𝑛 = ((VtxDeg‘𝐺)‘𝑘))) |
11 | 10 | rexbidv 3236 | . . . . . . . . . 10 ⊢ (𝑣 = 𝑘 → (∃𝑛 ∈ ℕ0 ((VtxDeg‘𝐺)‘𝑣) = 𝑛 ↔ ∃𝑛 ∈ ℕ0 𝑛 = ((VtxDeg‘𝐺)‘𝑘))) |
12 | 11 | rspcev 3529 | . . . . . . . . 9 ⊢ ((𝑘 ∈ 𝑉 ∧ ∃𝑛 ∈ ℕ0 𝑛 = ((VtxDeg‘𝐺)‘𝑘)) → ∃𝑣 ∈ 𝑉 ∃𝑛 ∈ ℕ0 ((VtxDeg‘𝐺)‘𝑣) = 𝑛) |
13 | 12 | expcom 406 | . . . . . . . 8 ⊢ (∃𝑛 ∈ ℕ0 𝑛 = ((VtxDeg‘𝐺)‘𝑘) → (𝑘 ∈ 𝑉 → ∃𝑣 ∈ 𝑉 ∃𝑛 ∈ ℕ0 ((VtxDeg‘𝐺)‘𝑣) = 𝑛)) |
14 | 7, 13 | sylbi 209 | . . . . . . 7 ⊢ (((VtxDeg‘𝐺)‘𝑘) ∈ ℕ0 → (𝑘 ∈ 𝑉 → ∃𝑣 ∈ 𝑉 ∃𝑛 ∈ ℕ0 ((VtxDeg‘𝐺)‘𝑣) = 𝑛)) |
15 | 14 | com12 32 | . . . . . 6 ⊢ (𝑘 ∈ 𝑉 → (((VtxDeg‘𝐺)‘𝑘) ∈ ℕ0 → ∃𝑣 ∈ 𝑉 ∃𝑛 ∈ ℕ0 ((VtxDeg‘𝐺)‘𝑣) = 𝑛)) |
16 | 6, 15 | syld 47 | . . . . 5 ⊢ (𝑘 ∈ 𝑉 → (∀𝑢 ∈ 𝑉 ((VtxDeg‘𝐺)‘𝑢) ∈ ℕ0 → ∃𝑣 ∈ 𝑉 ∃𝑛 ∈ ℕ0 ((VtxDeg‘𝐺)‘𝑣) = 𝑛)) |
17 | 3, 16 | syl5 34 | . . . 4 ⊢ (𝑘 ∈ 𝑉 → (𝐺 ∈ FinUSGraph → ∃𝑣 ∈ 𝑉 ∃𝑛 ∈ ℕ0 ((VtxDeg‘𝐺)‘𝑣) = 𝑛)) |
18 | 17 | exlimiv 1889 | . . 3 ⊢ (∃𝑘 𝑘 ∈ 𝑉 → (𝐺 ∈ FinUSGraph → ∃𝑣 ∈ 𝑉 ∃𝑛 ∈ ℕ0 ((VtxDeg‘𝐺)‘𝑣) = 𝑛)) |
19 | 1, 18 | sylbi 209 | . 2 ⊢ (𝑉 ≠ ∅ → (𝐺 ∈ FinUSGraph → ∃𝑣 ∈ 𝑉 ∃𝑛 ∈ ℕ0 ((VtxDeg‘𝐺)‘𝑣) = 𝑛)) |
20 | 19 | impcom 399 | 1 ⊢ ((𝐺 ∈ FinUSGraph ∧ 𝑉 ≠ ∅) → ∃𝑣 ∈ 𝑉 ∃𝑛 ∈ ℕ0 ((VtxDeg‘𝐺)‘𝑣) = 𝑛) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∧ wa 387 = wceq 1507 ∃wex 1742 ∈ wcel 2050 ≠ wne 2961 ∀wral 3082 ∃wrex 3083 ∅c0 4172 ‘cfv 6182 ℕ0cn0 11701 Vtxcvtx 26478 FinUSGraphcfusgr 26795 VtxDegcvtxdg 26944 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1758 ax-4 1772 ax-5 1869 ax-6 1928 ax-7 1965 ax-8 2052 ax-9 2059 ax-10 2079 ax-11 2093 ax-12 2106 ax-13 2301 ax-ext 2744 ax-rep 5043 ax-sep 5054 ax-nul 5061 ax-pow 5113 ax-pr 5180 ax-un 7273 ax-cnex 10385 ax-resscn 10386 ax-1cn 10387 ax-icn 10388 ax-addcl 10389 ax-addrcl 10390 ax-mulcl 10391 ax-mulrcl 10392 ax-mulcom 10393 ax-addass 10394 ax-mulass 10395 ax-distr 10396 ax-i2m1 10397 ax-1ne0 10398 ax-1rid 10399 ax-rnegex 10400 ax-rrecex 10401 ax-cnre 10402 ax-pre-lttri 10403 ax-pre-lttrn 10404 ax-pre-ltadd 10405 ax-pre-mulgt0 10406 |
This theorem depends on definitions: df-bi 199 df-an 388 df-or 834 df-3or 1069 df-3an 1070 df-tru 1510 df-ex 1743 df-nf 1747 df-sb 2016 df-mo 2547 df-eu 2584 df-clab 2753 df-cleq 2765 df-clel 2840 df-nfc 2912 df-ne 2962 df-nel 3068 df-ral 3087 df-rex 3088 df-reu 3089 df-rmo 3090 df-rab 3091 df-v 3411 df-sbc 3676 df-csb 3781 df-dif 3826 df-un 3828 df-in 3830 df-ss 3837 df-pss 3839 df-nul 4173 df-if 4345 df-pw 4418 df-sn 4436 df-pr 4438 df-tp 4440 df-op 4442 df-uni 4707 df-int 4744 df-iun 4788 df-br 4924 df-opab 4986 df-mpt 5003 df-tr 5025 df-id 5306 df-eprel 5311 df-po 5320 df-so 5321 df-fr 5360 df-we 5362 df-xp 5407 df-rel 5408 df-cnv 5409 df-co 5410 df-dm 5411 df-rn 5412 df-res 5413 df-ima 5414 df-pred 5980 df-ord 6026 df-on 6027 df-lim 6028 df-suc 6029 df-iota 6146 df-fun 6184 df-fn 6185 df-f 6186 df-f1 6187 df-fo 6188 df-f1o 6189 df-fv 6190 df-riota 6931 df-ov 6973 df-oprab 6974 df-mpo 6975 df-om 7391 df-1st 7495 df-2nd 7496 df-wrecs 7744 df-recs 7806 df-rdg 7844 df-1o 7899 df-2o 7900 df-oadd 7903 df-er 8083 df-en 8301 df-dom 8302 df-sdom 8303 df-fin 8304 df-dju 9118 df-card 9156 df-pnf 10470 df-mnf 10471 df-xr 10472 df-ltxr 10473 df-le 10474 df-sub 10666 df-neg 10667 df-nn 11434 df-2 11497 df-n0 11702 df-xnn0 11774 df-z 11788 df-uz 12053 df-xadd 12319 df-fz 12703 df-hash 13500 df-vtx 26480 df-iedg 26481 df-edg 26530 df-uhgr 26540 df-upgr 26564 df-umgr 26565 df-uspgr 26632 df-usgr 26633 df-fusgr 26796 df-vtxdg 26945 |
This theorem is referenced by: friendshipgt3 27949 |
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