P. 386 of Theorem List - Metamath Proof Explorer

Theorem List for Metamath Proof Explorer - 38501-38600   *Has distinct variable group(s)

Type	Label	Description
Statement
Syntax	cpre 38501	Extend the definition of a class to include the predecessor of a class.
class pre 𝑁
Syntax	cblockliftfix 38502	Extend the definition of a class to include the class of equilibrium block lifts.
class BlockLiftFix
Syntax	cshiftstable 38503	Extend the definition of a class to include the shift stability class.
class (𝑆 ShiftStable 𝐹)
Syntax	ccoss 38504	Extend the definition of a class to include the class of cosets by a class. (Read: the class of cosets by 𝑅.)
class ≀ 𝑅
Syntax	ccoels 38505	Extend the definition of a class to include the class of coelements on a class. (Read: the class of coelements on 𝐴.)
class ∼ 𝐴
Syntax	crels 38506	Extend the definition of a class to include the relation class.
class Rels
Syntax	cssr 38507	Extend the definition of a class to include the subset class.
class S
Syntax	crefs 38508	Extend the definition of a class to include the reflexivity class.
class Refs
Syntax	crefrels 38509	Extend the definition of a class to include the reflexive relations class.
class RefRels
Syntax	wrefrel 38510	Extend the definition of a wff to include the reflexive relation predicate. (Read: 𝑅 is a reflexive relation.)
wff RefRel 𝑅
Syntax	ccnvrefs 38511	Extend the definition of a class to include the converse reflexivity class.
class CnvRefs
Syntax	ccnvrefrels 38512	Extend the definition of a class to include the converse reflexive relations class.
class CnvRefRels
Syntax	wcnvrefrel 38513	Extend the definition of a wff to include the converse reflexive relation predicate. (Read: 𝑅 is a converse reflexive relation.)
wff CnvRefRel 𝑅
Syntax	csyms 38514	Extend the definition of a class to include the symmetry class.
class Syms
Syntax	csymrels 38515	Extend the definition of a class to include the symmetry relations class.
class SymRels
Syntax	wsymrel 38516	Extend the definition of a wff to include the symmetry relation predicate. (Read: 𝑅 is a symmetric relation.)
wff SymRel 𝑅
Syntax	ctrs 38517	Extend the definition of a class to include the transitivity class (but cf. the transitive class defined in df-tr 5193).
class Trs
Syntax	ctrrels 38518	Extend the definition of a class to include the transitive relations class.
class TrRels
Syntax	wtrrel 38519	Extend the definition of a wff to include the transitive relation predicate. (Read: 𝑅 is a transitive relation.)
wff TrRel 𝑅
Syntax	ceqvrels 38520	Extend the definition of a class to include the equivalence relations class.
class EqvRels
Syntax	weqvrel 38521	Extend the definition of a wff to include the equivalence relation predicate. (Read: 𝑅 is an equivalence relation.)
wff EqvRel 𝑅
Syntax	ccoeleqvrels 38522	Extend the definition of a class to include the coelement equivalence relations class.
class CoElEqvRels
Syntax	wcoeleqvrel 38523	Extend the definition of a wff to include the coelement equivalence relation predicate. (Read: the coelement equivalence relation on 𝐴.)
wff CoElEqvRel 𝐴
Syntax	credunds 38524	Extend the definition of a class to include the redundancy class.
class Redunds
Syntax	wredund 38525	Extend the definition of a wff to include the redundancy predicate. (Read: 𝐴 is redundant with respect to 𝐵 in 𝐶.)
wff 𝐴 Redund ⟨𝐵, 𝐶⟩
Syntax	wredundp 38526	Extend wff definition to include the redundancy operator for propositions.
wff redund (𝜑, 𝜓, 𝜒)
Syntax	cdmqss 38527	Extend the definition of a class to include the domain quotients class.
class DomainQss
Syntax	wdmqs 38528	Extend the definition of a wff to include the domain quotient predicate. (Read: the domain quotient of 𝑅 is 𝐴.)
wff 𝑅 DomainQs 𝐴
Syntax	cers 38529	Extend the definition of a class to include the equivalence relations on their domain quotients class.
class Ers
Syntax	werALTV 38530	Extend the definition of a wff to include the equivalence relation on its domain quotient predicate. (Read: 𝑅 is an equivalence relation on its domain quotient 𝐴.)
wff 𝑅 ErALTV 𝐴
Syntax	cpeters 38531	Extend the definition of a class to include the blocklift-stable equivalence relations class.
class PetErs
Syntax	cpet2ers 38532	Extend the definition of a class to include the grade- and blocklift-stable equivalence relations class.
class Pet2Ers
Syntax	ccomembers 38533	Extend the definition of a class to include the comember equivalence relations class.
class CoMembErs
Syntax	wcomember 38534	Extend the definition of a wff to include the comember equivalence relation predicate. (Read: the comember equivalence relation on 𝐴, or, the restricted coelement equivalence relation on its domain quotient 𝐴.)
wff CoMembEr 𝐴
Syntax	cfunss 38535	Extend the definition of a class to include the function set class.
class Funss
Syntax	cfunsALTV 38536	Extend the definition of a class to include the functions class, i.e., the function relations class.
class FunsALTV
Syntax	wfunALTV 38537	Extend the definition of a wff to include the function predicate, i.e., the function relation predicate. (Read: 𝐹 is a function.)
wff FunALTV 𝐹
Syntax	cdisjss 38538	Extend the definition of a class to include the disjoint set class.
class Disjss
Syntax	cdisjs 38539	Extend the definition of a class to include the disjoints class, i.e., the disjoint relations class.
class Disjs
Syntax	wdisjALTV 38540	Extend the definition of a wff to include the disjoint predicate, i.e., the disjoint relation predicate. (Read: 𝑅 is a disjoint.)
wff Disj 𝑅
Syntax	celdisjs 38541	Extend the definition of a class to include the disjoint elements class, i.e., the disjoint element relations class.
class ElDisjs
Syntax	weldisj 38542	Extend the definition of a wff to include the disjoint element predicate, i.e., the disjoint element relation predicate. (Read: the elements of 𝐴 are disjoint.)
wff ElDisj 𝐴
Syntax	wantisymrel 38543	Extend the definition of a wff to include the antisymmetry relation predicate. (Read: 𝑅 is an antisymmetric relation.)
wff AntisymRel 𝑅
Syntax	cparts 38544	Extend the definition of a class to include the partitions class, i.e., the partition relations class.
class Parts
Syntax	wpart 38545	Extend the definition of a wff to include the partition predicate, i.e., the partition relation predicate. (Read: 𝐴 is a partition by 𝑅.)
wff 𝑅 Part 𝐴
Syntax	cmembparts 38546	Extend the definition of a class to include the member partitions class, i.e., the member partition relations class.
class MembParts
Syntax	wmembpart 38547	Extend the definition of a wff to include the member partition predicate, i.e., the member partition relation predicate. (Read: 𝐴 is a member partition.)
wff MembPart 𝐴
Syntax	cpetparts 38548	Extend the definition of a class to include the blocklift-stable partitions class.
class PetParts
Syntax	cpet2parts 38549	Extend the definition of a class to include the grade- and blocklift-stable partitions class.
class Pet2Parts
21.26.2  Preparatory theorems
Theorem	el2v1 38550	New way (elv 3434, and the theorems beginning with "el2v" or "el3v") to shorten some proofs. (Contributed by Peter Mazsa, 23-Oct-2018.)
⊢ ((𝑥 ∈ V ∧ 𝜑) → 𝜓)    ⇒   ⊢ (𝜑 → 𝜓)
Theorem	el3v1 38551	New way (elv 3434, and the theorems beginning with "el2v" or "el3v") to shorten some proofs. (Contributed by Peter Mazsa, 16-Oct-2020.)
⊢ ((𝑥 ∈ V ∧ 𝜓 ∧ 𝜒) → 𝜃)    ⇒   ⊢ ((𝜓 ∧ 𝜒) → 𝜃)
Theorem	el3v2 38552	New way (elv 3434, and the theorems beginning with "el2v" or "el3v") to shorten some proofs. (Contributed by Peter Mazsa, 16-Oct-2020.)
⊢ ((𝜑 ∧ 𝑦 ∈ V ∧ 𝜒) → 𝜃)    ⇒   ⊢ ((𝜑 ∧ 𝜒) → 𝜃)
Theorem	el3v12 38553	New way (elv 3434, and the theorems beginning with "el2v" or "el3v") to shorten some proofs. (Contributed by Peter Mazsa, 11-Jul-2021.)
⊢ ((𝑥 ∈ V ∧ 𝑦 ∈ V ∧ 𝜒) → 𝜃)    ⇒   ⊢ (𝜒 → 𝜃)
Theorem	el3v13 38554	New way (elv 3434, and the theorems beginning with "el2v" or "el3v") to shorten some proofs. (Contributed by Peter Mazsa, 11-Jul-2021.)
⊢ ((𝑥 ∈ V ∧ 𝜓 ∧ 𝑧 ∈ V) → 𝜃)    ⇒   ⊢ (𝜓 → 𝜃)
Theorem	el3v23 38555	New way (elv 3434, and the theorems beginning with "el2v" or "el3v") to shorten some proofs. (Contributed by Peter Mazsa, 11-Jul-2021.)
⊢ ((𝜑 ∧ 𝑦 ∈ V ∧ 𝑧 ∈ V) → 𝜃)    ⇒   ⊢ (𝜑 → 𝜃)
Theorem	anan 38556	Multiple commutations in conjunction. (Contributed by Peter Mazsa, 7-Mar-2020.)
⊢ ((((𝜑 ∧ 𝜓) ∧ 𝜒) ∧ ((𝜑 ∧ 𝜃) ∧ 𝜏)) ↔ ((𝜓 ∧ 𝜃) ∧ (𝜑 ∧ (𝜒 ∧ 𝜏))))
Theorem	triantru3 38557	A wff is equivalent to its conjunctions with truths. (Contributed by Peter Mazsa, 30-Nov-2018.)
⊢ 𝜑    &   ⊢ 𝜓    ⇒   ⊢ (𝜒 ↔ (𝜑 ∧ 𝜓 ∧ 𝜒))
Theorem	biorfd 38558	A wff is equivalent to its disjunction with falsehood, deduction form. (Contributed by Peter Mazsa, 22-Aug-2023.)
⊢ (𝜑 → ¬ 𝜓)    ⇒   ⊢ (𝜑 → (𝜒 ↔ (𝜓 ∨ 𝜒)))
Theorem	eqbrtr 38559	Substitution of equal classes in binary relation. (Contributed by Peter Mazsa, 14-Jun-2024.)
⊢ ((𝐴 = 𝐵 ∧ 𝐵𝑅𝐶) → 𝐴𝑅𝐶)
Theorem	eqbrb 38560	Substitution of equal classes in a binary relation. (Contributed by Peter Mazsa, 14-Jun-2024.)
⊢ ((𝐴 = 𝐵 ∧ 𝐴𝑅𝐶) ↔ (𝐴 = 𝐵 ∧ 𝐵𝑅𝐶))
Theorem	eqeltr 38561	Substitution of equal classes into element relation. (Contributed by Peter Mazsa, 22-Jul-2017.)
⊢ ((𝐴 = 𝐵 ∧ 𝐵 ∈ 𝐶) → 𝐴 ∈ 𝐶)
Theorem	eqelb 38562	Substitution of equal classes into element relation. (Contributed by Peter Mazsa, 17-Jul-2019.)
⊢ ((𝐴 = 𝐵 ∧ 𝐴 ∈ 𝐶) ↔ (𝐴 = 𝐵 ∧ 𝐵 ∈ 𝐶))
Theorem	eqeqan2d 38563	Implication of introducing a new equality. (Contributed by Peter Mazsa, 17-Apr-2019.)
⊢ (𝜑 → 𝐶 = 𝐷)    ⇒   ⊢ ((𝐴 = 𝐵 ∧ 𝜑) → (𝐴 = 𝐶 ↔ 𝐵 = 𝐷))
Theorem	disjresin 38564	The restriction to a disjoint is the empty class. (Contributed by Peter Mazsa, 24-Jul-2024.)
⊢ ((𝐴 ∩ 𝐵) = ∅ → (𝑅 ↾ (𝐴 ∩ 𝐵)) = ∅)
Theorem	disjresdisj 38565	The intersection of restrictions to disjoint is the empty class. (Contributed by Peter Mazsa, 24-Jul-2024.)
⊢ ((𝐴 ∩ 𝐵) = ∅ → ((𝑅 ↾ 𝐴) ∩ (𝑅 ↾ 𝐵)) = ∅)
Theorem	disjresdif 38566	The difference between restrictions to disjoint is the first restriction. (Contributed by Peter Mazsa, 24-Jul-2024.)
⊢ ((𝐴 ∩ 𝐵) = ∅ → ((𝑅 ↾ 𝐴) ∖ (𝑅 ↾ 𝐵)) = (𝑅 ↾ 𝐴))
Theorem	disjresundif 38567	Lemma for ressucdifsn2 38808. (Contributed by Peter Mazsa, 24-Jul-2024.)
⊢ ((𝐴 ∩ 𝐵) = ∅ → ((𝑅 ↾ (𝐴 ∪ 𝐵)) ∖ (𝑅 ↾ 𝐵)) = (𝑅 ↾ 𝐴))
Theorem	inres2 38568	Two ways of expressing the restriction of an intersection. (Contributed by Peter Mazsa, 5-Jun-2021.)
⊢ ((𝑅 ↾ 𝐴) ∩ 𝑆) = ((𝑅 ∩ 𝑆) ↾ 𝐴)
Theorem	coideq 38569	Equality theorem for composition of two classes. (Contributed by Peter Mazsa, 23-Sep-2021.)
⊢ (𝐴 = 𝐵 → (𝐴 ∘ 𝐴) = (𝐵 ∘ 𝐵))
Theorem	nexmo1 38570	If there is no case where wff is true, it is true for at most one case. (Contributed by Peter Mazsa, 27-Sep-2021.)
⊢ (¬ ∃𝑥𝜑 → ∃*𝑥𝜑)
Theorem	eqab2 38571	Implication of a class abstraction. (Contributed by Peter Mazsa, 16-Apr-2019.)
⊢ (∀𝑥(𝑥 ∈ 𝐴 ↔ 𝜑) → ∀𝑥 ∈ 𝐴 𝜑)
Theorem	r2alan 38572*	Double restricted universal quantification, special case. (Contributed by Peter Mazsa, 17-Jun-2020.)
⊢ (∀𝑥∀𝑦(((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵) ∧ 𝜑) → 𝜓) ↔ ∀𝑥 ∈ 𝐴 ∀𝑦 ∈ 𝐵 (𝜑 → 𝜓))
Theorem	ssrabi 38573	Inference of restricted abstraction subclass from implication. (Contributed by Peter Mazsa, 26-Oct-2022.)
⊢ (𝜑 → 𝜓)    ⇒   ⊢ {𝑥 ∈ 𝐴 ∣ 𝜑} ⊆ {𝑥 ∈ 𝐴 ∣ 𝜓}
Theorem	rabimbieq 38574	Restricted equivalent wff's correspond to restricted class abstractions which are equal with the same class. (Contributed by Peter Mazsa, 22-Jul-2021.)
⊢ 𝐵 = {𝑥 ∈ 𝐴 ∣ 𝜑}    &   ⊢ (𝑥 ∈ 𝐴 → (𝜑 ↔ 𝜓))    ⇒   ⊢ 𝐵 = {𝑥 ∈ 𝐴 ∣ 𝜓}
Theorem	abeqin 38575*	Intersection with class abstraction. (Contributed by Peter Mazsa, 21-Jul-2021.)
⊢ 𝐴 = (𝐵 ∩ 𝐶)    &   ⊢ 𝐵 = {𝑥 ∣ 𝜑}    ⇒   ⊢ 𝐴 = {𝑥 ∈ 𝐶 ∣ 𝜑}
Theorem	abeqinbi 38576*	Intersection with class abstraction and equivalent wff's. (Contributed by Peter Mazsa, 21-Jul-2021.)
⊢ 𝐴 = (𝐵 ∩ 𝐶)    &   ⊢ 𝐵 = {𝑥 ∣ 𝜑}    &   ⊢ (𝑥 ∈ 𝐶 → (𝜑 ↔ 𝜓))    ⇒   ⊢ 𝐴 = {𝑥 ∈ 𝐶 ∣ 𝜓}
Theorem	eqrabi 38577*	Class element of a restricted class abstraction. (Contributed by Peter Mazsa, 24-Jul-2021.)
⊢ (𝑥 ∈ 𝐴 ↔ (𝑥 ∈ 𝐵 ∧ 𝜑))    ⇒   ⊢ 𝐴 = {𝑥 ∈ 𝐵 ∣ 𝜑}
Theorem	rabeqel 38578*	Class element of a restricted class abstraction. (Contributed by Peter Mazsa, 24-Jul-2021.)
⊢ 𝐵 = {𝑥 ∈ 𝐴 ∣ 𝜑}    &   ⊢ (𝑥 = 𝐶 → (𝜑 ↔ 𝜓))    ⇒   ⊢ (𝐶 ∈ 𝐵 ↔ (𝜓 ∧ 𝐶 ∈ 𝐴))
Theorem	eqrelf 38579*	The equality connective between relations. (Contributed by Peter Mazsa, 25-Jun-2019.)
⊢ Ⅎ𝑥𝐴    &   ⊢ Ⅎ𝑥𝐵    &   ⊢ Ⅎ𝑦𝐴    &   ⊢ Ⅎ𝑦𝐵    ⇒   ⊢ ((Rel 𝐴 ∧ Rel 𝐵) → (𝐴 = 𝐵 ↔ ∀𝑥∀𝑦(⟨𝑥, 𝑦⟩ ∈ 𝐴 ↔ ⟨𝑥, 𝑦⟩ ∈ 𝐵)))
Theorem	br1cnvinxp 38580	Binary relation on the converse of an intersection with a Cartesian product. (Contributed by Peter Mazsa, 27-Jul-2019.)
⊢ (𝐶◡(𝑅 ∩ (𝐴 × 𝐵))𝐷 ↔ ((𝐶 ∈ 𝐵 ∧ 𝐷 ∈ 𝐴) ∧ 𝐷𝑅𝐶))
Theorem	releleccnv 38581	Elementhood in a converse 𝑅-coset when 𝑅 is a relation. (Contributed by Peter Mazsa, 9-Dec-2018.)
⊢ (Rel 𝑅 → (𝐴 ∈ [𝐵]◡𝑅 ↔ 𝐴𝑅𝐵))
Theorem	releccnveq 38582*	Equality of converse 𝑅-coset and converse 𝑆-coset when 𝑅 and 𝑆 are relations. (Contributed by Peter Mazsa, 27-Jul-2019.)
⊢ ((Rel 𝑅 ∧ Rel 𝑆) → ([𝐴]◡𝑅 = [𝐵]◡𝑆 ↔ ∀𝑥(𝑥𝑅𝐴 ↔ 𝑥𝑆𝐵)))
Theorem	xpv 38583*	Cartesian product of a class and the universe. (Contributed by Peter Mazsa, 6-Oct-2020.)
⊢ (𝐴 × V) = {⟨𝑥, 𝑦⟩ ∣ 𝑥 ∈ 𝐴}
Theorem	vxp 38584*	Cartesian product of the universe and a class. (Contributed by Peter Mazsa, 3-Dec-2020.)
⊢ (V × 𝐴) = {⟨𝑥, 𝑦⟩ ∣ 𝑦 ∈ 𝐴}
Theorem	opelvvdif 38585	Negated elementhood of ordered pair. (Contributed by Peter Mazsa, 14-Jan-2019.)
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → (⟨𝐴, 𝐵⟩ ∈ ((V × V) ∖ 𝑅) ↔ ¬ ⟨𝐴, 𝐵⟩ ∈ 𝑅))
Theorem	vvdifopab 38586*	Ordered-pair class abstraction defined by a negation. (Contributed by Peter Mazsa, 25-Jun-2019.)
⊢ ((V × V) ∖ {⟨𝑥, 𝑦⟩ ∣ 𝜑}) = {⟨𝑥, 𝑦⟩ ∣ ¬ 𝜑}
Theorem	brvdif 38587	Binary relation with universal complement is the negation of the relation. (Contributed by Peter Mazsa, 1-Jul-2018.)
⊢ (𝐴(V ∖ 𝑅)𝐵 ↔ ¬ 𝐴𝑅𝐵)
Theorem	brvdif2 38588	Binary relation with universal complement. (Contributed by Peter Mazsa, 14-Jul-2018.)
⊢ (𝐴(V ∖ 𝑅)𝐵 ↔ ¬ ⟨𝐴, 𝐵⟩ ∈ 𝑅)
Theorem	brvvdif 38589	Binary relation with the complement under the universal class of ordered pairs. (Contributed by Peter Mazsa, 9-Nov-2018.)
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → (𝐴((V × V) ∖ 𝑅)𝐵 ↔ ¬ 𝐴𝑅𝐵))
Theorem	brvbrvvdif 38590	Binary relation with the complement under the universal class of ordered pairs is the same as with universal complement. (Contributed by Peter Mazsa, 28-Nov-2018.)
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → (𝐴((V × V) ∖ 𝑅)𝐵 ↔ 𝐴(V ∖ 𝑅)𝐵))
Theorem	brcnvep 38591	The converse of the binary epsilon relation. (Contributed by Peter Mazsa, 30-Jan-2018.)
⊢ (𝐴 ∈ 𝑉 → (𝐴◡ E 𝐵 ↔ 𝐵 ∈ 𝐴))
Theorem	elecALTV 38592	Elementhood in the 𝑅-coset of 𝐴. Theorem 72 of [Suppes] p. 82. (I think we should replace elecg 8688 with this original form of Suppes. Peter Mazsa). (Contributed by Mario Carneiro, 9-Jul-2014.)
⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊) → (𝐵 ∈ [𝐴]𝑅 ↔ 𝐴𝑅𝐵))
Theorem	brcnvepres 38593	Restricted converse epsilon binary relation. (Contributed by Peter Mazsa, 10-Feb-2018.)
⊢ ((𝐵 ∈ 𝑉 ∧ 𝐶 ∈ 𝑊) → (𝐵(◡ E ↾ 𝐴)𝐶 ↔ (𝐵 ∈ 𝐴 ∧ 𝐶 ∈ 𝐵)))
Theorem	brres2 38594	Binary relation on a restriction. (Contributed by Peter Mazsa, 2-Jan-2019.) (Revised by Peter Mazsa, 16-Dec-2021.)
⊢ (𝐵(𝑅 ↾ 𝐴)𝐶 ↔ 𝐵(𝑅 ∩ (𝐴 × ran (𝑅 ↾ 𝐴)))𝐶)
Theorem	br1cnvres 38595	Binary relation on the converse of a restriction. (Contributed by Peter Mazsa, 27-Jul-2019.)
⊢ (𝐵 ∈ 𝑉 → (𝐵◡(𝑅 ↾ 𝐴)𝐶 ↔ (𝐶 ∈ 𝐴 ∧ 𝐶𝑅𝐵)))
Theorem	elec1cnvres 38596	Elementhood in the converse restricted coset of 𝐵. (Contributed by Peter Mazsa, 21-Sep-2018.)
⊢ (𝐵 ∈ 𝑉 → (𝐶 ∈ [𝐵]◡(𝑅 ↾ 𝐴) ↔ (𝐶 ∈ 𝐴 ∧ 𝐶𝑅𝐵)))
Theorem	ec1cnvres 38597*	Converse restricted coset of 𝐵. (Contributed by Peter Mazsa, 22-Mar-2019.) (Revised by Peter Mazsa, 21-Oct-2021.)
⊢ (𝐵 ∈ 𝑉 → [𝐵]◡(𝑅 ↾ 𝐴) = {𝑥 ∈ 𝐴 ∣ 𝑥𝑅𝐵})
Theorem	eldmres 38598*	Elementhood in the domain of a restriction. (Contributed by Peter Mazsa, 9-Jan-2019.)
⊢ (𝐵 ∈ 𝑉 → (𝐵 ∈ dom (𝑅 ↾ 𝐴) ↔ (𝐵 ∈ 𝐴 ∧ ∃𝑦 𝐵𝑅𝑦)))
Theorem	elrnres 38599*	Element of the range of a restriction. (Contributed by Peter Mazsa, 26-Dec-2018.)
⊢ (𝐵 ∈ 𝑉 → (𝐵 ∈ ran (𝑅 ↾ 𝐴) ↔ ∃𝑥 ∈ 𝐴 𝑥𝑅𝐵))
Theorem	eldmressnALTV 38600	Element of the domain of a restriction to a singleton. (Contributed by Peter Mazsa, 12-Jun-2024.)
⊢ (𝐵 ∈ 𝑉 → (𝐵 ∈ dom (𝑅 ↾ {𝐴}) ↔ (𝐵 = 𝐴 ∧ 𝐴 ∈ dom 𝑅)))