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Theorem grpoideu 31144
Description: The left identity element of a group is unique. Lemma 2.2.1(a) of [Herstein] p. 55. (Contributed by NM, 14-Oct-2006.) (New usage is discouraged.)
Hypothesis
Ref Expression
grpfo.1 𝑋 = ran 𝐺
Assertion
Ref Expression
grpoideu (𝐺 ∈ GrpOp → ∃!𝑢 ∈ 𝑋 ∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥)
Distinct variable groups:   𝑥,𝑢,𝐺   𝑢,𝑋,𝑥

Proof of Theorem grpoideu
Dummy variables 𝑤 𝑦 𝑧 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 grpfo.1 . . . 4 𝑋 = ran 𝐺
21grpoidinv 31143 . . 3 (𝐺 ∈ GrpOp → ∃𝑢 ∈ 𝑋 ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢)))
3 simpll 779 . . . . . . . . 9 ((((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢)) → (𝑢𝐺𝑧) = 𝑧)
43ralimi 3103 . . . . . . . 8 (∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢)) → ∀𝑧 ∈ 𝑋 (𝑢𝐺𝑧) = 𝑧)
5 oveq2 7454 . . . . . . . . . 10 (𝑧 = 𝑥 → (𝑢𝐺𝑧) = (𝑢𝐺𝑥))
6 id 23 . . . . . . . . . 10 (𝑧 = 𝑥 → 𝑧 = 𝑥)
75, 6eqeq12d 2779 . . . . . . . . 9 (𝑧 = 𝑥 → ((𝑢𝐺𝑧) = 𝑧 ↔ (𝑢𝐺𝑥) = 𝑥))
87cbvralvw 3244 . . . . . . . 8 (∀𝑧 ∈ 𝑋 (𝑢𝐺𝑧) = 𝑧 ↔ ∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥)
94, 8sylib 221 . . . . . . 7 (∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢)) → ∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥)
109adantl 487 . . . . . 6 (((𝐺 ∈ GrpOp ∧ 𝑢 ∈ 𝑋) ∧ ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))) → ∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥)
119ad2antlr 740 . . . . . . . 8 ((((𝐺 ∈ GrpOp ∧ 𝑢 ∈ 𝑋) ∧ ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))) ∧ 𝑤 ∈ 𝑋) → ∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥)
12 simpr 490 . . . . . . . . . . . . . . . 16 ((((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢)) → ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))
1312ralimi 3103 . . . . . . . . . . . . . . 15 (∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢)) → ∀𝑧 ∈ 𝑋 ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))
14 oveq2 7454 . . . . . . . . . . . . . . . . . . . 20 (𝑧 = 𝑤 → (𝑦𝐺𝑧) = (𝑦𝐺𝑤))
1514eqeq1d 2765 . . . . . . . . . . . . . . . . . . 19 (𝑧 = 𝑤 → ((𝑦𝐺𝑧) = 𝑢 ↔ (𝑦𝐺𝑤) = 𝑢))
16 oveq1 7453 . . . . . . . . . . . . . . . . . . . 20 (𝑧 = 𝑤 → (𝑧𝐺𝑦) = (𝑤𝐺𝑦))
1716eqeq1d 2765 . . . . . . . . . . . . . . . . . . 19 (𝑧 = 𝑤 → ((𝑧𝐺𝑦) = 𝑢 ↔ (𝑤𝐺𝑦) = 𝑢))
1815, 17anbi12d 644 . . . . . . . . . . . . . . . . . 18 (𝑧 = 𝑤 → (((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢) ↔ ((𝑦𝐺𝑤) = 𝑢 ∧ (𝑤𝐺𝑦) = 𝑢)))
1918rexbidv 3190 . . . . . . . . . . . . . . . . 17 (𝑧 = 𝑤 → (∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢) ↔ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑤) = 𝑢 ∧ (𝑤𝐺𝑦) = 𝑢)))
2019rspcva 3578 . . . . . . . . . . . . . . . 16 ((𝑤 ∈ 𝑋 ∧ ∀𝑧 ∈ 𝑋 ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢)) → ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑤) = 𝑢 ∧ (𝑤𝐺𝑦) = 𝑢))
2120adantll 727 . . . . . . . . . . . . . . 15 (((𝐺 ∈ GrpOp ∧ 𝑤 ∈ 𝑋) ∧ ∀𝑧 ∈ 𝑋 ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢)) → ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑤) = 𝑢 ∧ (𝑤𝐺𝑦) = 𝑢))
2213, 21sylan2 605 . . . . . . . . . . . . . 14 (((𝐺 ∈ GrpOp ∧ 𝑤 ∈ 𝑋) ∧ ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))) → ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑤) = 𝑢 ∧ (𝑤𝐺𝑦) = 𝑢))
231grpoidinvlem4 31142 . . . . . . . . . . . . . 14 (((𝐺 ∈ GrpOp ∧ 𝑤 ∈ 𝑋) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑤) = 𝑢 ∧ (𝑤𝐺𝑦) = 𝑢)) → (𝑤𝐺𝑢) = (𝑢𝐺𝑤))
2422, 23syldan 603 . . . . . . . . . . . . 13 (((𝐺 ∈ GrpOp ∧ 𝑤 ∈ 𝑋) ∧ ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))) → (𝑤𝐺𝑢) = (𝑢𝐺𝑤))
2524an32s 665 . . . . . . . . . . . 12 (((𝐺 ∈ GrpOp ∧ ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))) ∧ 𝑤 ∈ 𝑋) → (𝑤𝐺𝑢) = (𝑢𝐺𝑤))
2625adantllr 732 . . . . . . . . . . 11 ((((𝐺 ∈ GrpOp ∧ 𝑢 ∈ 𝑋) ∧ ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))) ∧ 𝑤 ∈ 𝑋) → (𝑤𝐺𝑢) = (𝑢𝐺𝑤))
2726adantr 486 . . . . . . . . . 10 (((((𝐺 ∈ GrpOp ∧ 𝑢 ∈ 𝑋) ∧ ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))) ∧ 𝑤 ∈ 𝑋) ∧ (∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥 ∧ ∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥)) → (𝑤𝐺𝑢) = (𝑢𝐺𝑤))
28 oveq2 7454 . . . . . . . . . . . . . . 15 (𝑥 = 𝑢 → (𝑤𝐺𝑥) = (𝑤𝐺𝑢))
29 id 23 . . . . . . . . . . . . . . 15 (𝑥 = 𝑢 → 𝑥 = 𝑢)
3028, 29eqeq12d 2779 . . . . . . . . . . . . . 14 (𝑥 = 𝑢 → ((𝑤𝐺𝑥) = 𝑥 ↔ (𝑤𝐺𝑢) = 𝑢))
3130rspcva 3578 . . . . . . . . . . . . 13 ((𝑢 ∈ 𝑋 ∧ ∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥) → (𝑤𝐺𝑢) = 𝑢)
3231adantll 727 . . . . . . . . . . . 12 (((𝐺 ∈ GrpOp ∧ 𝑢 ∈ 𝑋) ∧ ∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥) → (𝑤𝐺𝑢) = 𝑢)
3332ad2ant2rl 762 . . . . . . . . . . 11 ((((𝐺 ∈ GrpOp ∧ 𝑢 ∈ 𝑋) ∧ 𝑤 ∈ 𝑋) ∧ (∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥 ∧ ∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥)) → (𝑤𝐺𝑢) = 𝑢)
3433adantllr 732 . . . . . . . . . 10 (((((𝐺 ∈ GrpOp ∧ 𝑢 ∈ 𝑋) ∧ ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))) ∧ 𝑤 ∈ 𝑋) ∧ (∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥 ∧ ∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥)) → (𝑤𝐺𝑢) = 𝑢)
35 oveq2 7454 . . . . . . . . . . . . 13 (𝑥 = 𝑤 → (𝑢𝐺𝑥) = (𝑢𝐺𝑤))
36 id 23 . . . . . . . . . . . . 13 (𝑥 = 𝑤 → 𝑥 = 𝑤)
3735, 36eqeq12d 2779 . . . . . . . . . . . 12 (𝑥 = 𝑤 → ((𝑢𝐺𝑥) = 𝑥 ↔ (𝑢𝐺𝑤) = 𝑤))
3837rspcva 3578 . . . . . . . . . . 11 ((𝑤 ∈ 𝑋 ∧ ∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥) → (𝑢𝐺𝑤) = 𝑤)
3938ad2ant2lr 761 . . . . . . . . . 10 (((((𝐺 ∈ GrpOp ∧ 𝑢 ∈ 𝑋) ∧ ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))) ∧ 𝑤 ∈ 𝑋) ∧ (∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥 ∧ ∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥)) → (𝑢𝐺𝑤) = 𝑤)
4027, 34, 393eqtr3d 2806 . . . . . . . . 9 (((((𝐺 ∈ GrpOp ∧ 𝑢 ∈ 𝑋) ∧ ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))) ∧ 𝑤 ∈ 𝑋) ∧ (∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥 ∧ ∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥)) → 𝑢 = 𝑤)
4140ex 418 . . . . . . . 8 ((((𝐺 ∈ GrpOp ∧ 𝑢 ∈ 𝑋) ∧ ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))) ∧ 𝑤 ∈ 𝑋) → ((∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥 ∧ ∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥) → 𝑢 = 𝑤))
4211, 41mpand 708 . . . . . . 7 ((((𝐺 ∈ GrpOp ∧ 𝑢 ∈ 𝑋) ∧ ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))) ∧ 𝑤 ∈ 𝑋) → (∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥 → 𝑢 = 𝑤))
4342ralrimiva 3158 . . . . . 6 (((𝐺 ∈ GrpOp ∧ 𝑢 ∈ 𝑋) ∧ ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))) → ∀𝑤 ∈ 𝑋 (∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥 → 𝑢 = 𝑤))
4410, 43jca 521 . . . . 5 (((𝐺 ∈ GrpOp ∧ 𝑢 ∈ 𝑋) ∧ ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢))) → (∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥 ∧ ∀𝑤 ∈ 𝑋 (∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥 → 𝑢 = 𝑤)))
4544ex 418 . . . 4 ((𝐺 ∈ GrpOp ∧ 𝑢 ∈ 𝑋) → (∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢)) → (∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥 ∧ ∀𝑤 ∈ 𝑋 (∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥 → 𝑢 = 𝑤))))
4645reximdva 3179 . . 3 (𝐺 ∈ GrpOp → (∃𝑢 ∈ 𝑋 ∀𝑧 ∈ 𝑋 (((𝑢𝐺𝑧) = 𝑧 ∧ (𝑧𝐺𝑢) = 𝑧) ∧ ∃𝑦 ∈ 𝑋 ((𝑦𝐺𝑧) = 𝑢 ∧ (𝑧𝐺𝑦) = 𝑢)) → ∃𝑢 ∈ 𝑋 (∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥 ∧ ∀𝑤 ∈ 𝑋 (∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥 → 𝑢 = 𝑤))))
472, 46mpd 16 . 2 (𝐺 ∈ GrpOp → ∃𝑢 ∈ 𝑋 (∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥 ∧ ∀𝑤 ∈ 𝑋 (∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥 → 𝑢 = 𝑤)))
48 oveq1 7453 . . . . 5 (𝑢 = 𝑤 → (𝑢𝐺𝑥) = (𝑤𝐺𝑥))
4948eqeq1d 2765 . . . 4 (𝑢 = 𝑤 → ((𝑢𝐺𝑥) = 𝑥 ↔ (𝑤𝐺𝑥) = 𝑥))
5049ralbidv 3189 . . 3 (𝑢 = 𝑤 → (∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥 ↔ ∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥))
5150reu8 3694 . 2 (∃!𝑢 ∈ 𝑋 ∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥 ↔ ∃𝑢 ∈ 𝑋 (∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥 ∧ ∀𝑤 ∈ 𝑋 (∀𝑥 ∈ 𝑋 (𝑤𝐺𝑥) = 𝑥 → 𝑢 = 𝑤)))
5247, 51sylibr 237 1 (𝐺 ∈ GrpOp → ∃!𝑢 ∈ 𝑋 ∀𝑥 ∈ 𝑋 (𝑢𝐺𝑥) = 𝑥)
Colors of variables:    wff setvar class
This proof depends on syntax axioms:   → wi 4   ∧ wa 401   = wceq 1570   ∈ wcel 2147  ∀wral 3080  ∃wrex 3090  ∃!wreu 3367  ran crn 5657  (class class class)co 7446  GrpOpcgr 31124
This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1945  ax-6 2002  ax-7 2043  ax-8 2149  ax-9 2157  ax-10 2180  ax-11 2197  ax-12 2216  ax-ext 2735  ax-sep 5253  ax-nul 5264  ax-pr 5396  ax-un 7778
This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-3an 1105  df-tru 1573  df-fal 1583  df-ex 1813  df-nf 1817  df-sb 2102  df-mo 2567  df-eu 2597  df-clab 2742  df-cleq 2755  df-clel 2839  df-nfc 2913  df-ne 2960  df-ral 3081  df-rex 3091  df-reu 3370  df-rab 3417  df-v 3456  df-sbc 3743  df-csb 3852  df-ss 3901  df-dif 4050  df-in 4094  df-un 4154  df-nul 4282  df-if 4486  df-sn 4589  df-pr 4591  df-op 4839  df-uni 4871  df-iun 4956  df-br 5107  df-opab 5172  df-mpt 5191  df-id 5551  df-xp 5662  df-rel 5663  df-cnv 5664  df-co 5665  df-dm 5666  df-rn 5667  df-iota 6515  df-fun 6563  df-fn 6564  df-f 6565  df-fo 6567  df-fv 6569  df-ov 7449  df-grpo 31128
This theorem is used by:  grpoidval  31148  grpoidcl  31149  grpoidinv2  31150  cnidOLD  31217  hilid  31796
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