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Theorem mgmb1mgm1 17874
 Description: The only magma with a base set consisting of one element is the trivial magma (at least if its operation is an internal binary operation). (Contributed by AV, 23-Jan-2020.) (Revised by AV, 7-Feb-2020.)
Hypotheses
Ref Expression
mgmb1mgm1.b 𝐵 = (Base‘𝑀)
mgmb1mgm1.p + = (+g𝑀)
Assertion
Ref Expression
mgmb1mgm1 ((𝑀 ∈ Mgm ∧ 𝑍𝐵+ Fn (𝐵 × 𝐵)) → (𝐵 = {𝑍} ↔ + = {⟨⟨𝑍, 𝑍⟩, 𝑍⟩}))

Proof of Theorem mgmb1mgm1
StepHypRef Expression
1 mgmb1mgm1.b . . . . . 6 𝐵 = (Base‘𝑀)
2 mgmb1mgm1.p . . . . . 6 + = (+g𝑀)
3 eqid 2798 . . . . . 6 (+𝑓𝑀) = (+𝑓𝑀)
41, 2, 3plusfeq 17869 . . . . 5 ( + Fn (𝐵 × 𝐵) → (+𝑓𝑀) = + )
51, 3mgmplusf 17871 . . . . . 6 (𝑀 ∈ Mgm → (+𝑓𝑀):(𝐵 × 𝐵)⟶𝐵)
6 feq1 6473 . . . . . 6 ((+𝑓𝑀) = + → ((+𝑓𝑀):(𝐵 × 𝐵)⟶𝐵+ :(𝐵 × 𝐵)⟶𝐵))
75, 6syl5ib 247 . . . . 5 ((+𝑓𝑀) = + → (𝑀 ∈ Mgm → + :(𝐵 × 𝐵)⟶𝐵))
84, 7syl 17 . . . 4 ( + Fn (𝐵 × 𝐵) → (𝑀 ∈ Mgm → + :(𝐵 × 𝐵)⟶𝐵))
98impcom 411 . . 3 ((𝑀 ∈ Mgm ∧ + Fn (𝐵 × 𝐵)) → + :(𝐵 × 𝐵)⟶𝐵)
1093adant2 1128 . 2 ((𝑀 ∈ Mgm ∧ 𝑍𝐵+ Fn (𝐵 × 𝐵)) → + :(𝐵 × 𝐵)⟶𝐵)
11 simp2 1134 . 2 ((𝑀 ∈ Mgm ∧ 𝑍𝐵+ Fn (𝐵 × 𝐵)) → 𝑍𝐵)
12 intopsn 17873 . 2 (( + :(𝐵 × 𝐵)⟶𝐵𝑍𝐵) → (𝐵 = {𝑍} ↔ + = {⟨⟨𝑍, 𝑍⟩, 𝑍⟩}))
1310, 11, 12syl2anc 587 1 ((𝑀 ∈ Mgm ∧ 𝑍𝐵+ Fn (𝐵 × 𝐵)) → (𝐵 = {𝑍} ↔ + = {⟨⟨𝑍, 𝑍⟩, 𝑍⟩}))
 Colors of variables: wff setvar class Syntax hints:   → wi 4   ↔ wb 209   ∧ w3a 1084   = wceq 1538   ∈ wcel 2111  {csn 4527  ⟨cop 4533   × cxp 5520   Fn wfn 6324  ⟶wf 6325  ‘cfv 6329  Basecbs 16492  +gcplusg 16574  +𝑓cplusf 17858  Mgmcmgm 17859 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1911  ax-6 1970  ax-7 2015  ax-8 2113  ax-9 2121  ax-10 2142  ax-11 2158  ax-12 2175  ax-ext 2770  ax-sep 5170  ax-nul 5177  ax-pow 5234  ax-pr 5298  ax-un 7451 This theorem depends on definitions:  df-bi 210  df-an 400  df-or 845  df-3an 1086  df-tru 1541  df-ex 1782  df-nf 1786  df-sb 2070  df-mo 2598  df-eu 2629  df-clab 2777  df-cleq 2791  df-clel 2870  df-nfc 2938  df-ne 2988  df-ral 3111  df-rex 3112  df-reu 3113  df-rab 3115  df-v 3443  df-sbc 3722  df-csb 3830  df-dif 3885  df-un 3887  df-in 3889  df-ss 3899  df-nul 4246  df-if 4428  df-pw 4501  df-sn 4528  df-pr 4530  df-op 4534  df-uni 4804  df-iun 4886  df-br 5034  df-opab 5096  df-mpt 5114  df-id 5428  df-xp 5528  df-rel 5529  df-cnv 5530  df-co 5531  df-dm 5532  df-rn 5533  df-res 5534  df-ima 5535  df-iota 6288  df-fun 6331  df-fn 6332  df-f 6333  df-f1 6334  df-fo 6335  df-f1o 6336  df-fv 6337  df-ov 7145  df-oprab 7146  df-mpo 7147  df-1st 7681  df-2nd 7682  df-plusf 17860  df-mgm 17861 This theorem is referenced by:  srg1zr  19290
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