![]() |
Metamath Proof Explorer |
< Previous
Next >
Nearby theorems |
|
Mirrors > Home > MPE Home > Th. List > frcond4 | Structured version Visualization version GIF version |
Description: The friendship condition, alternatively expressed by neighborhoods: in a friendship graph, the neighborhoods of two different vertices have exactly one vertex in common. (Contributed by Alexander van der Vekens, 19-Dec-2017.) (Revised by AV, 29-Mar-2021.) (Proof shortened by AV, 30-Dec-2021.) |
Ref | Expression |
---|---|
frcond1.v | ⊢ 𝑉 = (Vtx‘𝐺) |
frcond1.e | ⊢ 𝐸 = (Edg‘𝐺) |
Ref | Expression |
---|---|
frcond4 | ⊢ (𝐺 ∈ FriendGraph → ∀𝑘 ∈ 𝑉 ∀𝑙 ∈ (𝑉 ∖ {𝑘})∃𝑥 ∈ 𝑉 ((𝐺 NeighbVtx 𝑘) ∩ (𝐺 NeighbVtx 𝑙)) = {𝑥}) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | frcond1.v | . . . 4 ⊢ 𝑉 = (Vtx‘𝐺) | |
2 | frcond1.e | . . . 4 ⊢ 𝐸 = (Edg‘𝐺) | |
3 | 1, 2 | frcond3 29216 | . . 3 ⊢ (𝐺 ∈ FriendGraph → ((𝑘 ∈ 𝑉 ∧ 𝑙 ∈ 𝑉 ∧ 𝑘 ≠ 𝑙) → ∃𝑥 ∈ 𝑉 ((𝐺 NeighbVtx 𝑘) ∩ (𝐺 NeighbVtx 𝑙)) = {𝑥})) |
4 | eldifsn 4748 | . . . . . 6 ⊢ (𝑙 ∈ (𝑉 ∖ {𝑘}) ↔ (𝑙 ∈ 𝑉 ∧ 𝑙 ≠ 𝑘)) | |
5 | necom 2998 | . . . . . . . 8 ⊢ (𝑙 ≠ 𝑘 ↔ 𝑘 ≠ 𝑙) | |
6 | 5 | biimpi 215 | . . . . . . 7 ⊢ (𝑙 ≠ 𝑘 → 𝑘 ≠ 𝑙) |
7 | 6 | anim2i 618 | . . . . . 6 ⊢ ((𝑙 ∈ 𝑉 ∧ 𝑙 ≠ 𝑘) → (𝑙 ∈ 𝑉 ∧ 𝑘 ≠ 𝑙)) |
8 | 4, 7 | sylbi 216 | . . . . 5 ⊢ (𝑙 ∈ (𝑉 ∖ {𝑘}) → (𝑙 ∈ 𝑉 ∧ 𝑘 ≠ 𝑙)) |
9 | 8 | anim2i 618 | . . . 4 ⊢ ((𝑘 ∈ 𝑉 ∧ 𝑙 ∈ (𝑉 ∖ {𝑘})) → (𝑘 ∈ 𝑉 ∧ (𝑙 ∈ 𝑉 ∧ 𝑘 ≠ 𝑙))) |
10 | 3anass 1096 | . . . 4 ⊢ ((𝑘 ∈ 𝑉 ∧ 𝑙 ∈ 𝑉 ∧ 𝑘 ≠ 𝑙) ↔ (𝑘 ∈ 𝑉 ∧ (𝑙 ∈ 𝑉 ∧ 𝑘 ≠ 𝑙))) | |
11 | 9, 10 | sylibr 233 | . . 3 ⊢ ((𝑘 ∈ 𝑉 ∧ 𝑙 ∈ (𝑉 ∖ {𝑘})) → (𝑘 ∈ 𝑉 ∧ 𝑙 ∈ 𝑉 ∧ 𝑘 ≠ 𝑙)) |
12 | 3, 11 | impel 507 | . 2 ⊢ ((𝐺 ∈ FriendGraph ∧ (𝑘 ∈ 𝑉 ∧ 𝑙 ∈ (𝑉 ∖ {𝑘}))) → ∃𝑥 ∈ 𝑉 ((𝐺 NeighbVtx 𝑘) ∩ (𝐺 NeighbVtx 𝑙)) = {𝑥}) |
13 | 12 | ralrimivva 3198 | 1 ⊢ (𝐺 ∈ FriendGraph → ∀𝑘 ∈ 𝑉 ∀𝑙 ∈ (𝑉 ∖ {𝑘})∃𝑥 ∈ 𝑉 ((𝐺 NeighbVtx 𝑘) ∩ (𝐺 NeighbVtx 𝑙)) = {𝑥}) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∧ wa 397 ∧ w3a 1088 = wceq 1542 ∈ wcel 2107 ≠ wne 2944 ∀wral 3065 ∃wrex 3074 ∖ cdif 3908 ∩ cin 3910 {csn 4587 ‘cfv 6497 (class class class)co 7358 Vtxcvtx 27950 Edgcedg 28001 NeighbVtx cnbgr 28283 FriendGraph cfrgr 29205 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1798 ax-4 1812 ax-5 1914 ax-6 1972 ax-7 2012 ax-8 2109 ax-9 2117 ax-10 2138 ax-11 2155 ax-12 2172 ax-ext 2708 ax-sep 5257 ax-nul 5264 ax-pow 5321 ax-pr 5385 ax-un 7673 ax-cnex 11108 ax-resscn 11109 ax-1cn 11110 ax-icn 11111 ax-addcl 11112 ax-addrcl 11113 ax-mulcl 11114 ax-mulrcl 11115 ax-mulcom 11116 ax-addass 11117 ax-mulass 11118 ax-distr 11119 ax-i2m1 11120 ax-1ne0 11121 ax-1rid 11122 ax-rnegex 11123 ax-rrecex 11124 ax-cnre 11125 ax-pre-lttri 11126 ax-pre-lttrn 11127 ax-pre-ltadd 11128 ax-pre-mulgt0 11129 |
This theorem depends on definitions: df-bi 206 df-an 398 df-or 847 df-3or 1089 df-3an 1090 df-tru 1545 df-fal 1555 df-ex 1783 df-nf 1787 df-sb 2069 df-mo 2539 df-eu 2568 df-clab 2715 df-cleq 2729 df-clel 2815 df-nfc 2890 df-ne 2945 df-nel 3051 df-ral 3066 df-rex 3075 df-reu 3355 df-rab 3409 df-v 3448 df-sbc 3741 df-csb 3857 df-dif 3914 df-un 3916 df-in 3918 df-ss 3928 df-pss 3930 df-nul 4284 df-if 4488 df-pw 4563 df-sn 4588 df-pr 4590 df-op 4594 df-uni 4867 df-int 4909 df-iun 4957 df-br 5107 df-opab 5169 df-mpt 5190 df-tr 5224 df-id 5532 df-eprel 5538 df-po 5546 df-so 5547 df-fr 5589 df-we 5591 df-xp 5640 df-rel 5641 df-cnv 5642 df-co 5643 df-dm 5644 df-rn 5645 df-res 5646 df-ima 5647 df-pred 6254 df-ord 6321 df-on 6322 df-lim 6323 df-suc 6324 df-iota 6449 df-fun 6499 df-fn 6500 df-f 6501 df-f1 6502 df-fo 6503 df-f1o 6504 df-fv 6505 df-riota 7314 df-ov 7361 df-oprab 7362 df-mpo 7363 df-om 7804 df-1st 7922 df-2nd 7923 df-frecs 8213 df-wrecs 8244 df-recs 8318 df-rdg 8357 df-1o 8413 df-2o 8414 df-oadd 8417 df-er 8649 df-en 8885 df-dom 8886 df-sdom 8887 df-fin 8888 df-dju 9838 df-card 9876 df-pnf 11192 df-mnf 11193 df-xr 11194 df-ltxr 11195 df-le 11196 df-sub 11388 df-neg 11389 df-nn 12155 df-2 12217 df-n0 12415 df-xnn0 12487 df-z 12501 df-uz 12765 df-fz 13426 df-hash 14232 df-edg 28002 df-upgr 28036 df-umgr 28037 df-usgr 28105 df-nbgr 28284 df-frgr 29206 |
This theorem is referenced by: (None) |
Copyright terms: Public domain | W3C validator |