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Mirrors > Home > MPE Home > Th. List > frgrwopreg2 | Structured version Visualization version GIF version |
Description: According to statement 5 in [Huneke] p. 2: "If ... B is a singleton, then that singleton is a universal friend". (Contributed by Alexander van der Vekens, 1-Jan-2018.) (Proof shortened by AV, 4-Feb-2022.) |
Ref | Expression |
---|---|
frgrwopreg.v | ⊢ 𝑉 = (Vtx‘𝐺) |
frgrwopreg.d | ⊢ 𝐷 = (VtxDeg‘𝐺) |
frgrwopreg.a | ⊢ 𝐴 = {𝑥 ∈ 𝑉 ∣ (𝐷‘𝑥) = 𝐾} |
frgrwopreg.b | ⊢ 𝐵 = (𝑉 ∖ 𝐴) |
frgrwopreg.e | ⊢ 𝐸 = (Edg‘𝐺) |
Ref | Expression |
---|---|
frgrwopreg2 | ⊢ ((𝐺 ∈ FriendGraph ∧ (♯‘𝐵) = 1) → ∃𝑣 ∈ 𝑉 ∀𝑤 ∈ (𝑉 ∖ {𝑣}){𝑣, 𝑤} ∈ 𝐸) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | frgrwopreg.v | . . . . . 6 ⊢ 𝑉 = (Vtx‘𝐺) | |
2 | frgrwopreg.d | . . . . . 6 ⊢ 𝐷 = (VtxDeg‘𝐺) | |
3 | frgrwopreg.a | . . . . . 6 ⊢ 𝐴 = {𝑥 ∈ 𝑉 ∣ (𝐷‘𝑥) = 𝐾} | |
4 | frgrwopreg.b | . . . . . 6 ⊢ 𝐵 = (𝑉 ∖ 𝐴) | |
5 | 1, 2, 3, 4 | frgrwopreglem1 27779 | . . . . 5 ⊢ (𝐴 ∈ V ∧ 𝐵 ∈ V) |
6 | 5 | simpri 486 | . . . 4 ⊢ 𝐵 ∈ V |
7 | hash1snb 13632 | . . . 4 ⊢ (𝐵 ∈ V → ((♯‘𝐵) = 1 ↔ ∃𝑣 𝐵 = {𝑣})) | |
8 | 6, 7 | ax-mp 5 | . . 3 ⊢ ((♯‘𝐵) = 1 ↔ ∃𝑣 𝐵 = {𝑣}) |
9 | exsnrex 4531 | . . . . 5 ⊢ (∃𝑣 𝐵 = {𝑣} ↔ ∃𝑣 ∈ 𝐵 𝐵 = {𝑣}) | |
10 | difss 4035 | . . . . . . . 8 ⊢ (𝑉 ∖ 𝐴) ⊆ 𝑉 | |
11 | 4, 10 | eqsstri 3928 | . . . . . . 7 ⊢ 𝐵 ⊆ 𝑉 |
12 | ssrexv 3961 | . . . . . . 7 ⊢ (𝐵 ⊆ 𝑉 → (∃𝑣 ∈ 𝐵 𝐵 = {𝑣} → ∃𝑣 ∈ 𝑉 𝐵 = {𝑣})) | |
13 | 11, 12 | ax-mp 5 | . . . . . 6 ⊢ (∃𝑣 ∈ 𝐵 𝐵 = {𝑣} → ∃𝑣 ∈ 𝑉 𝐵 = {𝑣}) |
14 | frgrwopreg.e | . . . . . . . . 9 ⊢ 𝐸 = (Edg‘𝐺) | |
15 | 1, 2, 3, 4, 14 | frgrwopregbsn 27784 | . . . . . . . 8 ⊢ ((𝐺 ∈ FriendGraph ∧ 𝑣 ∈ 𝑉 ∧ 𝐵 = {𝑣}) → ∀𝑤 ∈ (𝑉 ∖ {𝑣}){𝑣, 𝑤} ∈ 𝐸) |
16 | 15 | 3expia 1114 | . . . . . . 7 ⊢ ((𝐺 ∈ FriendGraph ∧ 𝑣 ∈ 𝑉) → (𝐵 = {𝑣} → ∀𝑤 ∈ (𝑉 ∖ {𝑣}){𝑣, 𝑤} ∈ 𝐸)) |
17 | 16 | reximdva 3239 | . . . . . 6 ⊢ (𝐺 ∈ FriendGraph → (∃𝑣 ∈ 𝑉 𝐵 = {𝑣} → ∃𝑣 ∈ 𝑉 ∀𝑤 ∈ (𝑉 ∖ {𝑣}){𝑣, 𝑤} ∈ 𝐸)) |
18 | 13, 17 | syl5com 31 | . . . . 5 ⊢ (∃𝑣 ∈ 𝐵 𝐵 = {𝑣} → (𝐺 ∈ FriendGraph → ∃𝑣 ∈ 𝑉 ∀𝑤 ∈ (𝑉 ∖ {𝑣}){𝑣, 𝑤} ∈ 𝐸)) |
19 | 9, 18 | sylbi 218 | . . . 4 ⊢ (∃𝑣 𝐵 = {𝑣} → (𝐺 ∈ FriendGraph → ∃𝑣 ∈ 𝑉 ∀𝑤 ∈ (𝑉 ∖ {𝑣}){𝑣, 𝑤} ∈ 𝐸)) |
20 | 19 | com12 32 | . . 3 ⊢ (𝐺 ∈ FriendGraph → (∃𝑣 𝐵 = {𝑣} → ∃𝑣 ∈ 𝑉 ∀𝑤 ∈ (𝑉 ∖ {𝑣}){𝑣, 𝑤} ∈ 𝐸)) |
21 | 8, 20 | syl5bi 243 | . 2 ⊢ (𝐺 ∈ FriendGraph → ((♯‘𝐵) = 1 → ∃𝑣 ∈ 𝑉 ∀𝑤 ∈ (𝑉 ∖ {𝑣}){𝑣, 𝑤} ∈ 𝐸)) |
22 | 21 | imp 407 | 1 ⊢ ((𝐺 ∈ FriendGraph ∧ (♯‘𝐵) = 1) → ∃𝑣 ∈ 𝑉 ∀𝑤 ∈ (𝑉 ∖ {𝑣}){𝑣, 𝑤} ∈ 𝐸) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 207 ∧ wa 396 = wceq 1525 ∃wex 1765 ∈ wcel 2083 ∀wral 3107 ∃wrex 3108 {crab 3111 Vcvv 3440 ∖ cdif 3862 ⊆ wss 3865 {csn 4478 {cpr 4480 ‘cfv 6232 1c1 10391 ♯chash 13544 Vtxcvtx 26468 Edgcedg 26519 VtxDegcvtxdg 26934 FriendGraph cfrgr 27723 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1781 ax-4 1795 ax-5 1892 ax-6 1951 ax-7 1996 ax-8 2085 ax-9 2093 ax-10 2114 ax-11 2128 ax-12 2143 ax-13 2346 ax-ext 2771 ax-rep 5088 ax-sep 5101 ax-nul 5108 ax-pow 5164 ax-pr 5228 ax-un 7326 ax-cnex 10446 ax-resscn 10447 ax-1cn 10448 ax-icn 10449 ax-addcl 10450 ax-addrcl 10451 ax-mulcl 10452 ax-mulrcl 10453 ax-mulcom 10454 ax-addass 10455 ax-mulass 10456 ax-distr 10457 ax-i2m1 10458 ax-1ne0 10459 ax-1rid 10460 ax-rnegex 10461 ax-rrecex 10462 ax-cnre 10463 ax-pre-lttri 10464 ax-pre-lttrn 10465 ax-pre-ltadd 10466 ax-pre-mulgt0 10467 |
This theorem depends on definitions: df-bi 208 df-an 397 df-or 843 df-3or 1081 df-3an 1082 df-tru 1528 df-fal 1538 df-ex 1766 df-nf 1770 df-sb 2045 df-mo 2578 df-eu 2614 df-clab 2778 df-cleq 2790 df-clel 2865 df-nfc 2937 df-ne 2987 df-nel 3093 df-ral 3112 df-rex 3113 df-reu 3114 df-rmo 3115 df-rab 3116 df-v 3442 df-sbc 3712 df-csb 3818 df-dif 3868 df-un 3870 df-in 3872 df-ss 3880 df-pss 3882 df-nul 4218 df-if 4388 df-pw 4461 df-sn 4479 df-pr 4481 df-tp 4483 df-op 4485 df-uni 4752 df-int 4789 df-iun 4833 df-br 4969 df-opab 5031 df-mpt 5048 df-tr 5071 df-id 5355 df-eprel 5360 df-po 5369 df-so 5370 df-fr 5409 df-we 5411 df-xp 5456 df-rel 5457 df-cnv 5458 df-co 5459 df-dm 5460 df-rn 5461 df-res 5462 df-ima 5463 df-pred 6030 df-ord 6076 df-on 6077 df-lim 6078 df-suc 6079 df-iota 6196 df-fun 6234 df-fn 6235 df-f 6236 df-f1 6237 df-fo 6238 df-f1o 6239 df-fv 6240 df-riota 6984 df-ov 7026 df-oprab 7027 df-mpo 7028 df-om 7444 df-1st 7552 df-2nd 7553 df-wrecs 7805 df-recs 7867 df-rdg 7905 df-1o 7960 df-2o 7961 df-oadd 7964 df-er 8146 df-en 8365 df-dom 8366 df-sdom 8367 df-fin 8368 df-dju 9183 df-card 9221 df-pnf 10530 df-mnf 10531 df-xr 10532 df-ltxr 10533 df-le 10534 df-sub 10725 df-neg 10726 df-nn 11493 df-2 11554 df-n0 11752 df-xnn0 11822 df-z 11836 df-uz 12098 df-xadd 12362 df-fz 12747 df-hash 13545 df-edg 26520 df-uhgr 26530 df-ushgr 26531 df-upgr 26554 df-umgr 26555 df-uspgr 26622 df-usgr 26623 df-nbgr 26802 df-vtxdg 26935 df-frgr 27724 |
This theorem is referenced by: frgrregorufr0 27791 |
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