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Type | Label | Description |
---|---|---|
Statement | ||
Theorem | gsumwspan 18001* | The submonoid generated by a set of elements is precisely the set of elements which can be expressed as finite products of the generator. (Contributed by Stefan O'Rear, 22-Aug-2015.) |
⊢ 𝐵 = (Base‘𝑀) & ⊢ 𝐾 = (mrCls‘(SubMnd‘𝑀)) ⇒ ⊢ ((𝑀 ∈ Mnd ∧ 𝐺 ⊆ 𝐵) → (𝐾‘𝐺) = ran (𝑤 ∈ Word 𝐺 ↦ (𝑀 Σg 𝑤))) | ||
Syntax | cfrmd 18002 | Extend class definition with the free monoid construction. |
class freeMnd | ||
Syntax | cvrmd 18003 | Extend class notation with free monoid injection. |
class varFMnd | ||
Definition | df-frmd 18004 | Define a free monoid over a set 𝑖 of generators, defined as the set of finite strings on 𝐼 with the operation of concatenation. (Contributed by Mario Carneiro, 27-Sep-2015.) |
⊢ freeMnd = (𝑖 ∈ V ↦ {〈(Base‘ndx), Word 𝑖〉, 〈(+g‘ndx), ( ++ ↾ (Word 𝑖 × Word 𝑖))〉}) | ||
Definition | df-vrmd 18005* | Define a free monoid over a set 𝑖 of generators, defined as the set of finite strings on 𝐼 with the operation of concatenation. (Contributed by Mario Carneiro, 27-Sep-2015.) |
⊢ varFMnd = (𝑖 ∈ V ↦ (𝑗 ∈ 𝑖 ↦ 〈“𝑗”〉)) | ||
Theorem | frmdval 18006 | Value of the free monoid construction. (Contributed by Mario Carneiro, 27-Sep-2015.) |
⊢ 𝑀 = (freeMnd‘𝐼) & ⊢ (𝐼 ∈ 𝑉 → 𝐵 = Word 𝐼) & ⊢ + = ( ++ ↾ (𝐵 × 𝐵)) ⇒ ⊢ (𝐼 ∈ 𝑉 → 𝑀 = {〈(Base‘ndx), 𝐵〉, 〈(+g‘ndx), + 〉}) | ||
Theorem | frmdbas 18007 | The base set of a free monoid. (Contributed by Mario Carneiro, 27-Sep-2015.) (Revised by Mario Carneiro, 27-Feb-2016.) |
⊢ 𝑀 = (freeMnd‘𝐼) & ⊢ 𝐵 = (Base‘𝑀) ⇒ ⊢ (𝐼 ∈ 𝑉 → 𝐵 = Word 𝐼) | ||
Theorem | frmdelbas 18008 | An element of the base set of a free monoid is a string on the generators. (Contributed by Mario Carneiro, 27-Feb-2016.) |
⊢ 𝑀 = (freeMnd‘𝐼) & ⊢ 𝐵 = (Base‘𝑀) ⇒ ⊢ (𝑋 ∈ 𝐵 → 𝑋 ∈ Word 𝐼) | ||
Theorem | frmdplusg 18009 | The monoid operation of a free monoid. (Contributed by Mario Carneiro, 27-Sep-2015.) (Revised by Mario Carneiro, 27-Feb-2016.) |
⊢ 𝑀 = (freeMnd‘𝐼) & ⊢ 𝐵 = (Base‘𝑀) & ⊢ + = (+g‘𝑀) ⇒ ⊢ + = ( ++ ↾ (𝐵 × 𝐵)) | ||
Theorem | frmdadd 18010 | Value of the monoid operation of the free monoid construction. (Contributed by Mario Carneiro, 27-Sep-2015.) |
⊢ 𝑀 = (freeMnd‘𝐼) & ⊢ 𝐵 = (Base‘𝑀) & ⊢ + = (+g‘𝑀) ⇒ ⊢ ((𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵) → (𝑋 + 𝑌) = (𝑋 ++ 𝑌)) | ||
Theorem | vrmdfval 18011* | The canonical injection from the generating set 𝐼 to the base set of the free monoid. (Contributed by Mario Carneiro, 27-Feb-2016.) |
⊢ 𝑈 = (varFMnd‘𝐼) ⇒ ⊢ (𝐼 ∈ 𝑉 → 𝑈 = (𝑗 ∈ 𝐼 ↦ 〈“𝑗”〉)) | ||
Theorem | vrmdval 18012 | The value of the generating elements of a free monoid. (Contributed by Mario Carneiro, 27-Feb-2016.) |
⊢ 𝑈 = (varFMnd‘𝐼) ⇒ ⊢ ((𝐼 ∈ 𝑉 ∧ 𝐴 ∈ 𝐼) → (𝑈‘𝐴) = 〈“𝐴”〉) | ||
Theorem | vrmdf 18013 | The mapping from the index set to the generators is a function into the free monoid. (Contributed by Mario Carneiro, 27-Feb-2016.) |
⊢ 𝑈 = (varFMnd‘𝐼) ⇒ ⊢ (𝐼 ∈ 𝑉 → 𝑈:𝐼⟶Word 𝐼) | ||
Theorem | frmdmnd 18014 | A free monoid is a monoid. (Contributed by Mario Carneiro, 27-Sep-2015.) (Revised by Mario Carneiro, 27-Feb-2016.) |
⊢ 𝑀 = (freeMnd‘𝐼) ⇒ ⊢ (𝐼 ∈ 𝑉 → 𝑀 ∈ Mnd) | ||
Theorem | frmd0 18015 | The identity of the free monoid is the empty word. (Contributed by Mario Carneiro, 27-Sep-2015.) |
⊢ 𝑀 = (freeMnd‘𝐼) ⇒ ⊢ ∅ = (0g‘𝑀) | ||
Theorem | frmdsssubm 18016 | The set of words taking values in a subset is a (free) submonoid of the free monoid. (Contributed by Mario Carneiro, 27-Sep-2015.) (Revised by Mario Carneiro, 27-Feb-2016.) |
⊢ 𝑀 = (freeMnd‘𝐼) ⇒ ⊢ ((𝐼 ∈ 𝑉 ∧ 𝐽 ⊆ 𝐼) → Word 𝐽 ∈ (SubMnd‘𝑀)) | ||
Theorem | frmdgsum 18017 | Any word in a free monoid can be expressed as the sum of the singletons composing it. (Contributed by Mario Carneiro, 27-Sep-2015.) |
⊢ 𝑀 = (freeMnd‘𝐼) & ⊢ 𝑈 = (varFMnd‘𝐼) ⇒ ⊢ ((𝐼 ∈ 𝑉 ∧ 𝑊 ∈ Word 𝐼) → (𝑀 Σg (𝑈 ∘ 𝑊)) = 𝑊) | ||
Theorem | frmdss2 18018 | A subset of generators is contained in a submonoid iff the set of words on the generators is in the submonoid. This can be viewed as an elementary way of saying "the monoidal closure of 𝐽 is Word 𝐽". (Contributed by Mario Carneiro, 2-Oct-2015.) |
⊢ 𝑀 = (freeMnd‘𝐼) & ⊢ 𝑈 = (varFMnd‘𝐼) ⇒ ⊢ ((𝐼 ∈ 𝑉 ∧ 𝐽 ⊆ 𝐼 ∧ 𝐴 ∈ (SubMnd‘𝑀)) → ((𝑈 “ 𝐽) ⊆ 𝐴 ↔ Word 𝐽 ⊆ 𝐴)) | ||
Theorem | frmdup1 18019* | Any assignment of the generators to target elements can be extended (uniquely) to a homomorphism from a free monoid to an arbitrary other monoid. (Contributed by Mario Carneiro, 27-Sep-2015.) |
⊢ 𝑀 = (freeMnd‘𝐼) & ⊢ 𝐵 = (Base‘𝐺) & ⊢ 𝐸 = (𝑥 ∈ Word 𝐼 ↦ (𝐺 Σg (𝐴 ∘ 𝑥))) & ⊢ (𝜑 → 𝐺 ∈ Mnd) & ⊢ (𝜑 → 𝐼 ∈ 𝑋) & ⊢ (𝜑 → 𝐴:𝐼⟶𝐵) ⇒ ⊢ (𝜑 → 𝐸 ∈ (𝑀 MndHom 𝐺)) | ||
Theorem | frmdup2 18020* | The evaluation map has the intended behavior on the generators. (Contributed by Mario Carneiro, 27-Sep-2015.) |
⊢ 𝑀 = (freeMnd‘𝐼) & ⊢ 𝐵 = (Base‘𝐺) & ⊢ 𝐸 = (𝑥 ∈ Word 𝐼 ↦ (𝐺 Σg (𝐴 ∘ 𝑥))) & ⊢ (𝜑 → 𝐺 ∈ Mnd) & ⊢ (𝜑 → 𝐼 ∈ 𝑋) & ⊢ (𝜑 → 𝐴:𝐼⟶𝐵) & ⊢ 𝑈 = (varFMnd‘𝐼) & ⊢ (𝜑 → 𝑌 ∈ 𝐼) ⇒ ⊢ (𝜑 → (𝐸‘(𝑈‘𝑌)) = (𝐴‘𝑌)) | ||
Theorem | frmdup3lem 18021* | Lemma for frmdup3 18022. (Contributed by Mario Carneiro, 18-Jul-2016.) |
⊢ 𝑀 = (freeMnd‘𝐼) & ⊢ 𝐵 = (Base‘𝐺) & ⊢ 𝑈 = (varFMnd‘𝐼) ⇒ ⊢ (((𝐺 ∈ Mnd ∧ 𝐼 ∈ 𝑉 ∧ 𝐴:𝐼⟶𝐵) ∧ (𝐹 ∈ (𝑀 MndHom 𝐺) ∧ (𝐹 ∘ 𝑈) = 𝐴)) → 𝐹 = (𝑥 ∈ Word 𝐼 ↦ (𝐺 Σg (𝐴 ∘ 𝑥)))) | ||
Theorem | frmdup3 18022* | Universal property of the free monoid by existential uniqueness. (Contributed by Mario Carneiro, 2-Oct-2015.) (Revised by Mario Carneiro, 18-Jul-2016.) |
⊢ 𝑀 = (freeMnd‘𝐼) & ⊢ 𝐵 = (Base‘𝐺) & ⊢ 𝑈 = (varFMnd‘𝐼) ⇒ ⊢ ((𝐺 ∈ Mnd ∧ 𝐼 ∈ 𝑉 ∧ 𝐴:𝐼⟶𝐵) → ∃!𝑚 ∈ (𝑀 MndHom 𝐺)(𝑚 ∘ 𝑈) = 𝐴) | ||
Theorem | mgm2nsgrplem1 18023* | Lemma 1 for mgm2nsgrp 18027: 𝑀 is a magma, even if 𝐴 = 𝐵 (𝑀 is the trivial magma in this case, see mgmb1mgm1 17855). (Contributed by AV, 27-Jan-2020.) |
⊢ 𝑆 = {𝐴, 𝐵} & ⊢ (Base‘𝑀) = 𝑆 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝑆, 𝑦 ∈ 𝑆 ↦ if((𝑥 = 𝐴 ∧ 𝑦 = 𝐴), 𝐵, 𝐴)) ⇒ ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → 𝑀 ∈ Mgm) | ||
Theorem | mgm2nsgrplem2 18024* | Lemma 2 for mgm2nsgrp 18027. (Contributed by AV, 27-Jan-2020.) |
⊢ 𝑆 = {𝐴, 𝐵} & ⊢ (Base‘𝑀) = 𝑆 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝑆, 𝑦 ∈ 𝑆 ↦ if((𝑥 = 𝐴 ∧ 𝑦 = 𝐴), 𝐵, 𝐴)) & ⊢ ⚬ = (+g‘𝑀) ⇒ ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → ((𝐴 ⚬ 𝐴) ⚬ 𝐵) = 𝐴) | ||
Theorem | mgm2nsgrplem3 18025* | Lemma 3 for mgm2nsgrp 18027. (Contributed by AV, 28-Jan-2020.) |
⊢ 𝑆 = {𝐴, 𝐵} & ⊢ (Base‘𝑀) = 𝑆 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝑆, 𝑦 ∈ 𝑆 ↦ if((𝑥 = 𝐴 ∧ 𝑦 = 𝐴), 𝐵, 𝐴)) & ⊢ ⚬ = (+g‘𝑀) ⇒ ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → (𝐴 ⚬ (𝐴 ⚬ 𝐵)) = 𝐵) | ||
Theorem | mgm2nsgrplem4 18026* | Lemma 4 for mgm2nsgrp 18027: M is not a semigroup. (Contributed by AV, 28-Jan-2020.) (Proof shortened by AV, 31-Jan-2020.) |
⊢ 𝑆 = {𝐴, 𝐵} & ⊢ (Base‘𝑀) = 𝑆 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝑆, 𝑦 ∈ 𝑆 ↦ if((𝑥 = 𝐴 ∧ 𝑦 = 𝐴), 𝐵, 𝐴)) ⇒ ⊢ ((♯‘𝑆) = 2 → 𝑀 ∉ Smgrp) | ||
Theorem | mgm2nsgrp 18027* | A small magma (with two elements) which is not a semigroup. (Contributed by AV, 28-Jan-2020.) |
⊢ 𝑆 = {𝐴, 𝐵} & ⊢ (Base‘𝑀) = 𝑆 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝑆, 𝑦 ∈ 𝑆 ↦ if((𝑥 = 𝐴 ∧ 𝑦 = 𝐴), 𝐵, 𝐴)) ⇒ ⊢ ((♯‘𝑆) = 2 → (𝑀 ∈ Mgm ∧ 𝑀 ∉ Smgrp)) | ||
Theorem | sgrp2nmndlem1 18028* | Lemma 1 for sgrp2nmnd 18035: 𝑀 is a magma, even if 𝐴 = 𝐵 (𝑀 is the trivial magma in this case, see mgmb1mgm1 17855). (Contributed by AV, 29-Jan-2020.) |
⊢ 𝑆 = {𝐴, 𝐵} & ⊢ (Base‘𝑀) = 𝑆 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝑆, 𝑦 ∈ 𝑆 ↦ if(𝑥 = 𝐴, 𝐴, 𝐵)) ⇒ ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → 𝑀 ∈ Mgm) | ||
Theorem | sgrp2nmndlem2 18029* | Lemma 2 for sgrp2nmnd 18035. (Contributed by AV, 29-Jan-2020.) |
⊢ 𝑆 = {𝐴, 𝐵} & ⊢ (Base‘𝑀) = 𝑆 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝑆, 𝑦 ∈ 𝑆 ↦ if(𝑥 = 𝐴, 𝐴, 𝐵)) & ⊢ ⚬ = (+g‘𝑀) ⇒ ⊢ ((𝐴 ∈ 𝑆 ∧ 𝐶 ∈ 𝑆) → (𝐴 ⚬ 𝐶) = 𝐴) | ||
Theorem | sgrp2nmndlem3 18030* | Lemma 3 for sgrp2nmnd 18035. (Contributed by AV, 29-Jan-2020.) |
⊢ 𝑆 = {𝐴, 𝐵} & ⊢ (Base‘𝑀) = 𝑆 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝑆, 𝑦 ∈ 𝑆 ↦ if(𝑥 = 𝐴, 𝐴, 𝐵)) & ⊢ ⚬ = (+g‘𝑀) ⇒ ⊢ ((𝐶 ∈ 𝑆 ∧ 𝐵 ∈ 𝑆 ∧ 𝐴 ≠ 𝐵) → (𝐵 ⚬ 𝐶) = 𝐵) | ||
Theorem | sgrp2rid2 18031* | A small semigroup (with two elements) with two right identities which are different if 𝐴 ≠ 𝐵. (Contributed by AV, 10-Feb-2020.) |
⊢ 𝑆 = {𝐴, 𝐵} & ⊢ (Base‘𝑀) = 𝑆 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝑆, 𝑦 ∈ 𝑆 ↦ if(𝑥 = 𝐴, 𝐴, 𝐵)) & ⊢ ⚬ = (+g‘𝑀) ⇒ ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → ∀𝑥 ∈ 𝑆 ∀𝑦 ∈ 𝑆 (𝑦 ⚬ 𝑥) = 𝑦) | ||
Theorem | sgrp2rid2ex 18032* | A small semigroup (with two elements) with two right identities which are different. (Contributed by AV, 10-Feb-2020.) |
⊢ 𝑆 = {𝐴, 𝐵} & ⊢ (Base‘𝑀) = 𝑆 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝑆, 𝑦 ∈ 𝑆 ↦ if(𝑥 = 𝐴, 𝐴, 𝐵)) & ⊢ ⚬ = (+g‘𝑀) ⇒ ⊢ ((♯‘𝑆) = 2 → ∃𝑥 ∈ 𝑆 ∃𝑧 ∈ 𝑆 ∀𝑦 ∈ 𝑆 (𝑥 ≠ 𝑧 ∧ (𝑦 ⚬ 𝑥) = 𝑦 ∧ (𝑦 ⚬ 𝑧) = 𝑦)) | ||
Theorem | sgrp2nmndlem4 18033* | Lemma 4 for sgrp2nmnd 18035: M is a semigroup. (Contributed by AV, 29-Jan-2020.) |
⊢ 𝑆 = {𝐴, 𝐵} & ⊢ (Base‘𝑀) = 𝑆 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝑆, 𝑦 ∈ 𝑆 ↦ if(𝑥 = 𝐴, 𝐴, 𝐵)) ⇒ ⊢ ((♯‘𝑆) = 2 → 𝑀 ∈ Smgrp) | ||
Theorem | sgrp2nmndlem5 18034* | Lemma 5 for sgrp2nmnd 18035: M is not a monoid. (Contributed by AV, 29-Jan-2020.) |
⊢ 𝑆 = {𝐴, 𝐵} & ⊢ (Base‘𝑀) = 𝑆 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝑆, 𝑦 ∈ 𝑆 ↦ if(𝑥 = 𝐴, 𝐴, 𝐵)) ⇒ ⊢ ((♯‘𝑆) = 2 → 𝑀 ∉ Mnd) | ||
Theorem | sgrp2nmnd 18035* | A small semigroup (with two elements) which is not a monoid. (Contributed by AV, 26-Jan-2020.) |
⊢ 𝑆 = {𝐴, 𝐵} & ⊢ (Base‘𝑀) = 𝑆 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝑆, 𝑦 ∈ 𝑆 ↦ if(𝑥 = 𝐴, 𝐴, 𝐵)) ⇒ ⊢ ((♯‘𝑆) = 2 → (𝑀 ∈ Smgrp ∧ 𝑀 ∉ Mnd)) | ||
Theorem | mgmnsgrpex 18036 | There is a magma which is not a semigroup. (Contributed by AV, 29-Jan-2020.) |
⊢ ∃𝑚 ∈ Mgm 𝑚 ∉ Smgrp | ||
Theorem | sgrpnmndex 18037 | There is a semigroup which is not a monoid. (Contributed by AV, 29-Jan-2020.) |
⊢ ∃𝑚 ∈ Smgrp 𝑚 ∉ Mnd | ||
Theorem | sgrpssmgm 18038 | The class of all semigroups is a proper subclass of the class of all magmas. (Contributed by AV, 29-Jan-2020.) |
⊢ Smgrp ⊊ Mgm | ||
Theorem | mndsssgrp 18039 | The class of all monoids is a proper subclass of the class of all semigroups. (Contributed by AV, 29-Jan-2020.) |
⊢ Mnd ⊊ Smgrp | ||
Theorem | pwmndgplus 18040* | The operation of the monoid of the power set of a class 𝐴 under union. (Contributed by AV, 27-Feb-2024.) |
⊢ (Base‘𝑀) = 𝒫 𝐴 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝒫 𝐴, 𝑦 ∈ 𝒫 𝐴 ↦ (𝑥 ∪ 𝑦)) ⇒ ⊢ ((𝑋 ∈ 𝒫 𝐴 ∧ 𝑌 ∈ 𝒫 𝐴) → (𝑋(+g‘𝑀)𝑌) = (𝑋 ∪ 𝑌)) | ||
Theorem | pwmndid 18041* | The identity of the monoid of the power set of a class 𝐴 under union is the empty set. (Contributed by AV, 27-Feb-2024.) |
⊢ (Base‘𝑀) = 𝒫 𝐴 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝒫 𝐴, 𝑦 ∈ 𝒫 𝐴 ↦ (𝑥 ∪ 𝑦)) ⇒ ⊢ (0g‘𝑀) = ∅ | ||
Theorem | pwmnd 18042* | The power set of a class 𝐴 is a monoid under union. (Contributed by AV, 27-Feb-2024.) |
⊢ (Base‘𝑀) = 𝒫 𝐴 & ⊢ (+g‘𝑀) = (𝑥 ∈ 𝒫 𝐴, 𝑦 ∈ 𝒫 𝐴 ↦ (𝑥 ∪ 𝑦)) ⇒ ⊢ 𝑀 ∈ Mnd | ||
Syntax | cgrp 18043 | Extend class notation with class of all groups. |
class Grp | ||
Syntax | cminusg 18044 | Extend class notation with inverse of group element. |
class invg | ||
Syntax | csg 18045 | Extend class notation with group subtraction (or division) operation. |
class -g | ||
Definition | df-grp 18046* | Define class of all groups. A group is a monoid (df-mnd 17902) whose internal operation is such that every element admits a left inverse (which can be proven to be a two-sided inverse). Thus, a group 𝐺 is an algebraic structure formed from a base set of elements (notated (Base‘𝐺) per df-base 16479) and an internal group operation (notated (+g‘𝐺) per df-plusg 16568). The operation combines any two elements of the group base set and must satisfy the 4 group axioms: closure (the result of the group operation must always be a member of the base set, see grpcl 18051), associativity (so ((𝑎+g𝑏)+g𝑐) = (𝑎+g(𝑏+g𝑐)) for any a, b, c, see grpass 18052), identity (there must be an element 𝑒 = (0g‘𝐺) such that 𝑒+g𝑎 = 𝑎+g𝑒 = 𝑎 for any a), and inverse (for each element a in the base set, there must be an element 𝑏 = invg𝑎 in the base set such that 𝑎+g𝑏 = 𝑏+g𝑎 = 𝑒). It can be proven that the identity element is unique (grpideu 18054). Groups need not be commutative; a commutative group is an Abelian group (see df-abl 18840). Subgroups can often be formed from groups, see df-subg 18216. An example of an (Abelian) group is the set of complex numbers ℂ over the group operation + (addition), as proven in cnaddablx 18919; an Abelian group is a group as proven in ablgrp 18842. Other structures include groups, including unital rings (df-ring 19230) and fields (df-field 19436). (Contributed by NM, 17-Oct-2012.) (Revised by Mario Carneiro, 6-Jan-2015.) |
⊢ Grp = {𝑔 ∈ Mnd ∣ ∀𝑎 ∈ (Base‘𝑔)∃𝑚 ∈ (Base‘𝑔)(𝑚(+g‘𝑔)𝑎) = (0g‘𝑔)} | ||
Definition | df-minusg 18047* | Define inverse of group element. (Contributed by NM, 24-Aug-2011.) |
⊢ invg = (𝑔 ∈ V ↦ (𝑥 ∈ (Base‘𝑔) ↦ (℩𝑤 ∈ (Base‘𝑔)(𝑤(+g‘𝑔)𝑥) = (0g‘𝑔)))) | ||
Definition | df-sbg 18048* | Define group subtraction (also called division for multiplicative groups). (Contributed by NM, 31-Mar-2014.) |
⊢ -g = (𝑔 ∈ V ↦ (𝑥 ∈ (Base‘𝑔), 𝑦 ∈ (Base‘𝑔) ↦ (𝑥(+g‘𝑔)((invg‘𝑔)‘𝑦)))) | ||
Theorem | isgrp 18049* | The predicate "is a group." (This theorem demonstrates the use of symbols as variable names, first proposed by FL in 2010.) (Contributed by NM, 17-Oct-2012.) (Revised by Mario Carneiro, 6-Jan-2015.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp ↔ (𝐺 ∈ Mnd ∧ ∀𝑎 ∈ 𝐵 ∃𝑚 ∈ 𝐵 (𝑚 + 𝑎) = 0 )) | ||
Theorem | grpmnd 18050 | A group is a monoid. (Contributed by Mario Carneiro, 6-Jan-2015.) |
⊢ (𝐺 ∈ Grp → 𝐺 ∈ Mnd) | ||
Theorem | grpcl 18051 | Closure of the operation of a group. (Contributed by NM, 14-Aug-2011.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵) → (𝑋 + 𝑌) ∈ 𝐵) | ||
Theorem | grpass 18052 | A group operation is associative. (Contributed by NM, 14-Aug-2011.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ (𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ∧ 𝑍 ∈ 𝐵)) → ((𝑋 + 𝑌) + 𝑍) = (𝑋 + (𝑌 + 𝑍))) | ||
Theorem | grpinvex 18053* | Every member of a group has a left inverse. (Contributed by NM, 16-Aug-2011.) (Revised by Mario Carneiro, 6-Jan-2015.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵) → ∃𝑦 ∈ 𝐵 (𝑦 + 𝑋) = 0 ) | ||
Theorem | grpideu 18054* | The two-sided identity element of a group is unique. Lemma 2.2.1(a) of [Herstein] p. 55. (Contributed by NM, 16-Aug-2011.) (Revised by Mario Carneiro, 8-Dec-2014.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp → ∃!𝑢 ∈ 𝐵 ∀𝑥 ∈ 𝐵 ((𝑢 + 𝑥) = 𝑥 ∧ (𝑥 + 𝑢) = 𝑥)) | ||
Theorem | grpplusf 18055 | The group addition operation is a function. (Contributed by Mario Carneiro, 14-Aug-2015.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ 𝐹 = (+𝑓‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp → 𝐹:(𝐵 × 𝐵)⟶𝐵) | ||
Theorem | grpplusfo 18056 | The group addition operation is a function onto the base set/set of group elements. (Contributed by NM, 30-Oct-2006.) (Revised by AV, 30-Aug-2021.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ 𝐹 = (+𝑓‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp → 𝐹:(𝐵 × 𝐵)–onto→𝐵) | ||
Theorem | resgrpplusfrn 18057 | The underlying set of a group operation which is a restriction of a structure. (Contributed by Paul Chapman, 25-Mar-2008.) (Revised by AV, 30-Aug-2021.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ 𝐻 = (𝐺 ↾s 𝑆) & ⊢ 𝐹 = (+𝑓‘𝐻) ⇒ ⊢ ((𝐻 ∈ Grp ∧ 𝑆 ⊆ 𝐵) → 𝑆 = ran 𝐹) | ||
Theorem | grppropd 18058* | If two structures have the same group components (properties), one is a group iff the other one is. (Contributed by Stefan O'Rear, 27-Nov-2014.) (Revised by Mario Carneiro, 2-Oct-2015.) |
⊢ (𝜑 → 𝐵 = (Base‘𝐾)) & ⊢ (𝜑 → 𝐵 = (Base‘𝐿)) & ⊢ ((𝜑 ∧ (𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵)) → (𝑥(+g‘𝐾)𝑦) = (𝑥(+g‘𝐿)𝑦)) ⇒ ⊢ (𝜑 → (𝐾 ∈ Grp ↔ 𝐿 ∈ Grp)) | ||
Theorem | grpprop 18059 | If two structures have the same group components (properties), one is a group iff the other one is. (Contributed by NM, 11-Oct-2013.) |
⊢ (Base‘𝐾) = (Base‘𝐿) & ⊢ (+g‘𝐾) = (+g‘𝐿) ⇒ ⊢ (𝐾 ∈ Grp ↔ 𝐿 ∈ Grp) | ||
Theorem | grppropstr 18060 | Generalize a specific 2-element group 𝐿 to show that any set 𝐾 with the same (relevant) properties is also a group. (Contributed by NM, 28-Oct-2012.) (Revised by Mario Carneiro, 6-Jan-2015.) |
⊢ (Base‘𝐾) = 𝐵 & ⊢ (+g‘𝐾) = + & ⊢ 𝐿 = {〈(Base‘ndx), 𝐵〉, 〈(+g‘ndx), + 〉} ⇒ ⊢ (𝐾 ∈ Grp ↔ 𝐿 ∈ Grp) | ||
Theorem | grpss 18061 | Show that a structure extending a constructed group (e.g., a ring) is also a group. This allows us to prove that a constructed potential ring 𝑅 is a group before we know that it is also a ring. (Theorem ringgrp 19233, on the other hand, requires that we know in advance that 𝑅 is a ring.) (Contributed by NM, 11-Oct-2013.) |
⊢ 𝐺 = {〈(Base‘ndx), 𝐵〉, 〈(+g‘ndx), + 〉} & ⊢ 𝑅 ∈ V & ⊢ 𝐺 ⊆ 𝑅 & ⊢ Fun 𝑅 ⇒ ⊢ (𝐺 ∈ Grp ↔ 𝑅 ∈ Grp) | ||
Theorem | isgrpd2e 18062* | Deduce a group from its properties. In this version of isgrpd2 18063, we don't assume there is an expression for the inverse of 𝑥. (Contributed by NM, 10-Aug-2013.) |
⊢ (𝜑 → 𝐵 = (Base‘𝐺)) & ⊢ (𝜑 → + = (+g‘𝐺)) & ⊢ (𝜑 → 0 = (0g‘𝐺)) & ⊢ (𝜑 → 𝐺 ∈ Mnd) & ⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵) → ∃𝑦 ∈ 𝐵 (𝑦 + 𝑥) = 0 ) ⇒ ⊢ (𝜑 → 𝐺 ∈ Grp) | ||
Theorem | isgrpd2 18063* | Deduce a group from its properties. 𝑁 (negative) is normally dependent on 𝑥 i.e. read it as 𝑁(𝑥). Note: normally we don't use a 𝜑 antecedent on hypotheses that name structure components, since they can be eliminated with eqid 2821, but we make an exception for theorems such as isgrpd2 18063, ismndd 17923, and islmodd 19571 since theorems using them often rewrite the structure components. (Contributed by NM, 10-Aug-2013.) |
⊢ (𝜑 → 𝐵 = (Base‘𝐺)) & ⊢ (𝜑 → + = (+g‘𝐺)) & ⊢ (𝜑 → 0 = (0g‘𝐺)) & ⊢ (𝜑 → 𝐺 ∈ Mnd) & ⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵) → 𝑁 ∈ 𝐵) & ⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵) → (𝑁 + 𝑥) = 0 ) ⇒ ⊢ (𝜑 → 𝐺 ∈ Grp) | ||
Theorem | isgrpde 18064* | Deduce a group from its properties. In this version of isgrpd 18065, we don't assume there is an expression for the inverse of 𝑥. (Contributed by NM, 6-Jan-2015.) |
⊢ (𝜑 → 𝐵 = (Base‘𝐺)) & ⊢ (𝜑 → + = (+g‘𝐺)) & ⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) → (𝑥 + 𝑦) ∈ 𝐵) & ⊢ ((𝜑 ∧ (𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵 ∧ 𝑧 ∈ 𝐵)) → ((𝑥 + 𝑦) + 𝑧) = (𝑥 + (𝑦 + 𝑧))) & ⊢ (𝜑 → 0 ∈ 𝐵) & ⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵) → ( 0 + 𝑥) = 𝑥) & ⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵) → ∃𝑦 ∈ 𝐵 (𝑦 + 𝑥) = 0 ) ⇒ ⊢ (𝜑 → 𝐺 ∈ Grp) | ||
Theorem | isgrpd 18065* | Deduce a group from its properties. Unlike isgrpd2 18063, this one goes straight from the base properties rather than going through Mnd. 𝑁 (negative) is normally dependent on 𝑥 i.e. read it as 𝑁(𝑥). (Contributed by NM, 6-Jun-2013.) (Revised by Mario Carneiro, 6-Jan-2015.) |
⊢ (𝜑 → 𝐵 = (Base‘𝐺)) & ⊢ (𝜑 → + = (+g‘𝐺)) & ⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) → (𝑥 + 𝑦) ∈ 𝐵) & ⊢ ((𝜑 ∧ (𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵 ∧ 𝑧 ∈ 𝐵)) → ((𝑥 + 𝑦) + 𝑧) = (𝑥 + (𝑦 + 𝑧))) & ⊢ (𝜑 → 0 ∈ 𝐵) & ⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵) → ( 0 + 𝑥) = 𝑥) & ⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵) → 𝑁 ∈ 𝐵) & ⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵) → (𝑁 + 𝑥) = 0 ) ⇒ ⊢ (𝜑 → 𝐺 ∈ Grp) | ||
Theorem | isgrpi 18066* | Properties that determine a group. 𝑁 (negative) is normally dependent on 𝑥 i.e. read it as 𝑁(𝑥). (Contributed by NM, 3-Sep-2011.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) → (𝑥 + 𝑦) ∈ 𝐵) & ⊢ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵 ∧ 𝑧 ∈ 𝐵) → ((𝑥 + 𝑦) + 𝑧) = (𝑥 + (𝑦 + 𝑧))) & ⊢ 0 ∈ 𝐵 & ⊢ (𝑥 ∈ 𝐵 → ( 0 + 𝑥) = 𝑥) & ⊢ (𝑥 ∈ 𝐵 → 𝑁 ∈ 𝐵) & ⊢ (𝑥 ∈ 𝐵 → (𝑁 + 𝑥) = 0 ) ⇒ ⊢ 𝐺 ∈ Grp | ||
Theorem | grpsgrp 18067 | A group is a semigroup. (Contributed by AV, 28-Aug-2021.) |
⊢ (𝐺 ∈ Grp → 𝐺 ∈ Smgrp) | ||
Theorem | dfgrp2 18068* | Alternate definition of a group as semigroup with a left identity and a left inverse for each element. This "definition" is weaker than df-grp 18046, based on the definition of a monoid which provides a left and a right identity. (Contributed by AV, 28-Aug-2021.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp ↔ (𝐺 ∈ Smgrp ∧ ∃𝑛 ∈ 𝐵 ∀𝑥 ∈ 𝐵 ((𝑛 + 𝑥) = 𝑥 ∧ ∃𝑖 ∈ 𝐵 (𝑖 + 𝑥) = 𝑛))) | ||
Theorem | dfgrp2e 18069* | Alternate definition of a group as a set with a closed, associative operation, a left identity and a left inverse for each element. Alternate definition in [Lang] p. 7. (Contributed by NM, 10-Oct-2006.) (Revised by AV, 28-Aug-2021.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp ↔ (∀𝑥 ∈ 𝐵 ∀𝑦 ∈ 𝐵 ((𝑥 + 𝑦) ∈ 𝐵 ∧ ∀𝑧 ∈ 𝐵 ((𝑥 + 𝑦) + 𝑧) = (𝑥 + (𝑦 + 𝑧))) ∧ ∃𝑛 ∈ 𝐵 ∀𝑥 ∈ 𝐵 ((𝑛 + 𝑥) = 𝑥 ∧ ∃𝑖 ∈ 𝐵 (𝑖 + 𝑥) = 𝑛))) | ||
Theorem | isgrpix 18070* | Properties that determine a group. Read 𝑁 as 𝑁(𝑥). Note: This theorem has hard-coded structure indices for demonstration purposes. It is not intended for general use. (New usage is discouraged.) (Contributed by NM, 4-Sep-2011.) |
⊢ 𝐵 ∈ V & ⊢ + ∈ V & ⊢ 𝐺 = {〈1, 𝐵〉, 〈2, + 〉} & ⊢ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵) → (𝑥 + 𝑦) ∈ 𝐵) & ⊢ ((𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵 ∧ 𝑧 ∈ 𝐵) → ((𝑥 + 𝑦) + 𝑧) = (𝑥 + (𝑦 + 𝑧))) & ⊢ 0 ∈ 𝐵 & ⊢ (𝑥 ∈ 𝐵 → ( 0 + 𝑥) = 𝑥) & ⊢ (𝑥 ∈ 𝐵 → 𝑁 ∈ 𝐵) & ⊢ (𝑥 ∈ 𝐵 → (𝑁 + 𝑥) = 0 ) ⇒ ⊢ 𝐺 ∈ Grp | ||
Theorem | grpidcl 18071 | The identity element of a group belongs to the group. (Contributed by NM, 27-Aug-2011.) (Revised by Mario Carneiro, 27-Dec-2014.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ 0 = (0g‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp → 0 ∈ 𝐵) | ||
Theorem | grpbn0 18072 | The base set of a group is not empty. (Contributed by Szymon Jaroszewicz, 3-Apr-2007.) |
⊢ 𝐵 = (Base‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp → 𝐵 ≠ ∅) | ||
Theorem | grplid 18073 | The identity element of a group is a left identity. (Contributed by NM, 18-Aug-2011.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵) → ( 0 + 𝑋) = 𝑋) | ||
Theorem | grprid 18074 | The identity element of a group is a right identity. (Contributed by NM, 18-Aug-2011.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵) → (𝑋 + 0 ) = 𝑋) | ||
Theorem | grpn0 18075 | A group is not empty. (Contributed by Szymon Jaroszewicz, 3-Apr-2007.) (Revised by Mario Carneiro, 2-Dec-2014.) |
⊢ (𝐺 ∈ Grp → 𝐺 ≠ ∅) | ||
Theorem | hashfingrpnn 18076 | A finite group has positive integer size. (Contributed by Rohan Ridenour, 3-Aug-2023.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ (𝜑 → 𝐺 ∈ Grp) & ⊢ (𝜑 → 𝐵 ∈ Fin) ⇒ ⊢ (𝜑 → (♯‘𝐵) ∈ ℕ) | ||
Theorem | grprcan 18077 | Right cancellation law for groups. (Contributed by NM, 24-Aug-2011.) (Proof shortened by Mario Carneiro, 6-Jan-2015.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ (𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ∧ 𝑍 ∈ 𝐵)) → ((𝑋 + 𝑍) = (𝑌 + 𝑍) ↔ 𝑋 = 𝑌)) | ||
Theorem | grpinveu 18078* | The left inverse element of a group is unique. Lemma 2.2.1(b) of [Herstein] p. 55. (Contributed by NM, 24-Aug-2011.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵) → ∃!𝑦 ∈ 𝐵 (𝑦 + 𝑋) = 0 ) | ||
Theorem | grpid 18079 | Two ways of saying that an element of a group is the identity element. Provides a convenient way to compute the value of the identity element. (Contributed by NM, 24-Aug-2011.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵) → ((𝑋 + 𝑋) = 𝑋 ↔ 0 = 𝑋)) | ||
Theorem | isgrpid2 18080 | Properties showing that an element 𝑍 is the identity element of a group. (Contributed by NM, 7-Aug-2013.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp → ((𝑍 ∈ 𝐵 ∧ (𝑍 + 𝑍) = 𝑍) ↔ 0 = 𝑍)) | ||
Theorem | grpidd2 18081* | Deduce the identity element of a group from its properties. Useful in conjunction with isgrpd 18065. (Contributed by Mario Carneiro, 14-Jun-2015.) |
⊢ (𝜑 → 𝐵 = (Base‘𝐺)) & ⊢ (𝜑 → + = (+g‘𝐺)) & ⊢ (𝜑 → 0 ∈ 𝐵) & ⊢ ((𝜑 ∧ 𝑥 ∈ 𝐵) → ( 0 + 𝑥) = 𝑥) & ⊢ (𝜑 → 𝐺 ∈ Grp) ⇒ ⊢ (𝜑 → 0 = (0g‘𝐺)) | ||
Theorem | grpinvfval 18082* | The inverse function of a group. For a shorter proof using ax-rep 5182, see grpinvfvalALT 18083. (Contributed by NM, 24-Aug-2011.) (Revised by Mario Carneiro, 7-Aug-2013.) Remove dependency on ax-rep 5182. (Revised by Rohan Ridenour, 13-Aug-2023.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) & ⊢ 𝑁 = (invg‘𝐺) ⇒ ⊢ 𝑁 = (𝑥 ∈ 𝐵 ↦ (℩𝑦 ∈ 𝐵 (𝑦 + 𝑥) = 0 )) | ||
Theorem | grpinvfvalALT 18083* | Shorter proof of grpinvfval 18082 using ax-rep 5182. (Contributed by NM, 24-Aug-2011.) (Revised by Mario Carneiro, 7-Aug-2013.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) & ⊢ 𝑁 = (invg‘𝐺) ⇒ ⊢ 𝑁 = (𝑥 ∈ 𝐵 ↦ (℩𝑦 ∈ 𝐵 (𝑦 + 𝑥) = 0 )) | ||
Theorem | grpinvval 18084* | The inverse of a group element. (Contributed by NM, 24-Aug-2011.) (Revised by Mario Carneiro, 7-Aug-2013.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) & ⊢ 𝑁 = (invg‘𝐺) ⇒ ⊢ (𝑋 ∈ 𝐵 → (𝑁‘𝑋) = (℩𝑦 ∈ 𝐵 (𝑦 + 𝑋) = 0 )) | ||
Theorem | grpinvfn 18085 | Functionality of the group inverse function. (Contributed by Stefan O'Rear, 21-Mar-2015.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ 𝑁 = (invg‘𝐺) ⇒ ⊢ 𝑁 Fn 𝐵 | ||
Theorem | grpinvfvi 18086 | The group inverse function is compatible with identity-function protection. (Contributed by Stefan O'Rear, 21-Mar-2015.) |
⊢ 𝑁 = (invg‘𝐺) ⇒ ⊢ 𝑁 = (invg‘( I ‘𝐺)) | ||
Theorem | grpsubfval 18087* | Group subtraction (division) operation. For a shorter proof using ax-rep 5182, see grpsubfvalALT 18088. (Contributed by NM, 31-Mar-2014.) (Revised by Stefan O'Rear, 27-Mar-2015.) Remove dependency on ax-rep 5182. (Revised by Rohan Ridenour, 17-Aug-2023.) (Proof shortened by AV, 19-Feb-2024.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 𝐼 = (invg‘𝐺) & ⊢ − = (-g‘𝐺) ⇒ ⊢ − = (𝑥 ∈ 𝐵, 𝑦 ∈ 𝐵 ↦ (𝑥 + (𝐼‘𝑦))) | ||
Theorem | grpsubfvalALT 18088* | Shorter proof of grpsubfval 18087 using ax-rep 5182. (Contributed by NM, 31-Mar-2014.) (Revised by Stefan O'Rear, 27-Mar-2015.) (Proof shortened by AV, 19-Feb-2024.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 𝐼 = (invg‘𝐺) & ⊢ − = (-g‘𝐺) ⇒ ⊢ − = (𝑥 ∈ 𝐵, 𝑦 ∈ 𝐵 ↦ (𝑥 + (𝐼‘𝑦))) | ||
Theorem | grpsubval 18089 | Group subtraction (division) operation. (Contributed by NM, 31-Mar-2014.) (Revised by Mario Carneiro, 13-Dec-2014.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 𝐼 = (invg‘𝐺) & ⊢ − = (-g‘𝐺) ⇒ ⊢ ((𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵) → (𝑋 − 𝑌) = (𝑋 + (𝐼‘𝑌))) | ||
Theorem | grpinvf 18090 | The group inversion operation is a function on the base set. (Contributed by Mario Carneiro, 4-May-2015.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ 𝑁 = (invg‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp → 𝑁:𝐵⟶𝐵) | ||
Theorem | grpinvcl 18091 | A group element's inverse is a group element. (Contributed by NM, 24-Aug-2011.) (Revised by Mario Carneiro, 4-May-2015.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ 𝑁 = (invg‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵) → (𝑁‘𝑋) ∈ 𝐵) | ||
Theorem | grplinv 18092 | The left inverse of a group element. (Contributed by NM, 24-Aug-2011.) (Revised by Mario Carneiro, 6-Jan-2015.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) & ⊢ 𝑁 = (invg‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵) → ((𝑁‘𝑋) + 𝑋) = 0 ) | ||
Theorem | grprinv 18093 | The right inverse of a group element. (Contributed by NM, 24-Aug-2011.) (Revised by Mario Carneiro, 6-Jan-2015.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) & ⊢ 𝑁 = (invg‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵) → (𝑋 + (𝑁‘𝑋)) = 0 ) | ||
Theorem | grpinvid1 18094 | The inverse of a group element expressed in terms of the identity element. (Contributed by NM, 24-Aug-2011.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) & ⊢ 𝑁 = (invg‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵) → ((𝑁‘𝑋) = 𝑌 ↔ (𝑋 + 𝑌) = 0 )) | ||
Theorem | grpinvid2 18095 | The inverse of a group element expressed in terms of the identity element. (Contributed by NM, 24-Aug-2011.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) & ⊢ 𝑁 = (invg‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵) → ((𝑁‘𝑋) = 𝑌 ↔ (𝑌 + 𝑋) = 0 )) | ||
Theorem | isgrpinv 18096* | Properties showing that a function 𝑀 is the inverse function of a group. (Contributed by NM, 7-Aug-2013.) (Revised by Mario Carneiro, 2-Oct-2015.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) & ⊢ 𝑁 = (invg‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp → ((𝑀:𝐵⟶𝐵 ∧ ∀𝑥 ∈ 𝐵 ((𝑀‘𝑥) + 𝑥) = 0 ) ↔ 𝑁 = 𝑀)) | ||
Theorem | grplrinv 18097* | In a group, every member has a left and right inverse. (Contributed by AV, 1-Sep-2021.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp → ∀𝑥 ∈ 𝐵 ∃𝑦 ∈ 𝐵 ((𝑦 + 𝑥) = 0 ∧ (𝑥 + 𝑦) = 0 )) | ||
Theorem | grpidinv2 18098* | A group's properties using the explicit identity element. (Contributed by NM, 5-Feb-2010.) (Revised by AV, 1-Sep-2021.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) & ⊢ 0 = (0g‘𝐺) ⇒ ⊢ ((𝐺 ∈ Grp ∧ 𝐴 ∈ 𝐵) → ((( 0 + 𝐴) = 𝐴 ∧ (𝐴 + 0 ) = 𝐴) ∧ ∃𝑦 ∈ 𝐵 ((𝑦 + 𝐴) = 0 ∧ (𝐴 + 𝑦) = 0 ))) | ||
Theorem | grpidinv 18099* | A group has a left and right identity element, and every member has a left and right inverse. (Contributed by NM, 14-Oct-2006.) (Revised by AV, 1-Sep-2021.) |
⊢ 𝐵 = (Base‘𝐺) & ⊢ + = (+g‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp → ∃𝑢 ∈ 𝐵 ∀𝑥 ∈ 𝐵 (((𝑢 + 𝑥) = 𝑥 ∧ (𝑥 + 𝑢) = 𝑥) ∧ ∃𝑦 ∈ 𝐵 ((𝑦 + 𝑥) = 𝑢 ∧ (𝑥 + 𝑦) = 𝑢))) | ||
Theorem | grpinvid 18100 | The inverse of the identity element of a group. (Contributed by NM, 24-Aug-2011.) |
⊢ 0 = (0g‘𝐺) & ⊢ 𝑁 = (invg‘𝐺) ⇒ ⊢ (𝐺 ∈ Grp → (𝑁‘ 0 ) = 0 ) |
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