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Theorem List for Intuitionistic Logic Explorer - 7001-7100   *Has distinct variable group(s)
TypeLabelDescription
Statement
 
Theoremsuplubti 7001* A supremum is the least upper bound. See also supclti 6999 and supubti 7000. (Contributed by Jim Kingdon, 24-Nov-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   &    |-  ( ph  ->  E. x  e.  A  ( A. y  e.  B  -.  x R y  /\  A. y  e.  A  ( y R x  ->  E. z  e.  B  y R z ) ) )   =>    |-  ( ph  ->  ( ( C  e.  A  /\  C R sup ( B ,  A ,  R ) )  ->  E. z  e.  B  C R z ) )
 
Theoremsuplub2ti 7002* Bidirectional form of suplubti 7001. (Contributed by Jim Kingdon, 17-Jan-2022.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   &    |-  ( ph  ->  E. x  e.  A  ( A. y  e.  B  -.  x R y  /\  A. y  e.  A  ( y R x  ->  E. z  e.  B  y R z ) ) )   &    |-  ( ph  ->  R  Or  A )   &    |-  ( ph  ->  B  C_  A )   =>    |-  ( ( ph  /\  C  e.  A )  ->  ( C R sup ( B ,  A ,  R ) 
 <-> 
 E. z  e.  B  C R z ) )
 
Theoremsupelti 7003* Supremum membership in a set. (Contributed by Jim Kingdon, 16-Jan-2022.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   &    |-  ( ph  ->  E. x  e.  C  ( A. y  e.  B  -.  x R y  /\  A. y  e.  A  ( y R x  ->  E. z  e.  B  y R z ) ) )   &    |-  ( ph  ->  C  C_  A )   =>    |-  ( ph  ->  sup ( B ,  A ,  R )  e.  C )
 
Theoremsup00 7004 The supremum under an empty base set is always the empty set. (Contributed by AV, 4-Sep-2020.)
 |- 
 sup ( B ,  (/)
 ,  R )  =  (/)
 
Theoremsupmaxti 7005* The greatest element of a set is its supremum. Note that the converse is not true; the supremum might not be an element of the set considered. (Contributed by Jim Kingdon, 24-Nov-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   &    |-  ( ph  ->  C  e.  A )   &    |-  ( ph  ->  C  e.  B )   &    |-  (
 ( ph  /\  y  e.  B )  ->  -.  C R y )   =>    |-  ( ph  ->  sup ( B ,  A ,  R )  =  C )
 
Theoremsupsnti 7006* The supremum of a singleton. (Contributed by Jim Kingdon, 26-Nov-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   &    |-  ( ph  ->  B  e.  A )   =>    |-  ( ph  ->  sup ( { B } ,  A ,  R )  =  B )
 
Theoremisotilem 7007* Lemma for isoti 7008. (Contributed by Jim Kingdon, 26-Nov-2021.)
 |-  ( F  Isom  R ,  S  ( A ,  B )  ->  ( A. x  e.  B  A. y  e.  B  ( x  =  y  <->  ( -.  x S y  /\  -.  y S x ) )  ->  A. u  e.  A  A. v  e.  A  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) ) )
 
Theoremisoti 7008* An isomorphism preserves tightness. (Contributed by Jim Kingdon, 26-Nov-2021.)
 |-  ( F  Isom  R ,  S  ( A ,  B )  ->  ( A. u  e.  A  A. v  e.  A  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) )  <->  A. u  e.  B  A. v  e.  B  ( u  =  v  <->  ( -.  u S v  /\  -.  v S u ) ) ) )
 
Theoremsupisolem 7009* Lemma for supisoti 7011. (Contributed by Mario Carneiro, 24-Dec-2016.)
 |-  ( ph  ->  F  Isom  R ,  S  ( A ,  B ) )   &    |-  ( ph  ->  C 
 C_  A )   =>    |-  ( ( ph  /\  D  e.  A ) 
 ->  ( ( A. y  e.  C  -.  D R y  /\  A. y  e.  A  ( y R D  ->  E. z  e.  C  y R z ) )  <->  ( A. w  e.  ( F " C )  -.  ( F `  D ) S w 
 /\  A. w  e.  B  ( w S ( F `
  D )  ->  E. v  e.  ( F " C ) w S v ) ) ) )
 
Theoremsupisoex 7010* Lemma for supisoti 7011. (Contributed by Mario Carneiro, 24-Dec-2016.)
 |-  ( ph  ->  F  Isom  R ,  S  ( A ,  B ) )   &    |-  ( ph  ->  C 
 C_  A )   &    |-  ( ph  ->  E. x  e.  A  ( A. y  e.  C  -.  x R y  /\  A. y  e.  A  ( y R x  ->  E. z  e.  C  y R z ) ) )   =>    |-  ( ph  ->  E. u  e.  B  ( A. w  e.  ( F " C )  -.  u S w 
 /\  A. w  e.  B  ( w S u  ->  E. v  e.  ( F " C ) w S v ) ) )
 
Theoremsupisoti 7011* Image of a supremum under an isomorphism. (Contributed by Jim Kingdon, 26-Nov-2021.)
 |-  ( ph  ->  F  Isom  R ,  S  ( A ,  B ) )   &    |-  ( ph  ->  C 
 C_  A )   &    |-  ( ph  ->  E. x  e.  A  ( A. y  e.  C  -.  x R y  /\  A. y  e.  A  ( y R x  ->  E. z  e.  C  y R z ) ) )   &    |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A ) )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   =>    |-  ( ph  ->  sup ( ( F " C ) ,  B ,  S )  =  ( F ` 
 sup ( C ,  A ,  R )
 ) )
 
Theoreminfeq1 7012 Equality theorem for infimum. (Contributed by AV, 2-Sep-2020.)
 |-  ( B  =  C  -> inf ( B ,  A ,  R )  = inf ( C ,  A ,  R ) )
 
Theoreminfeq1d 7013 Equality deduction for infimum. (Contributed by AV, 2-Sep-2020.)
 |-  ( ph  ->  B  =  C )   =>    |-  ( ph  -> inf ( B ,  A ,  R )  = inf ( C ,  A ,  R ) )
 
Theoreminfeq1i 7014 Equality inference for infimum. (Contributed by AV, 2-Sep-2020.)
 |-  B  =  C   =>    |- inf ( B ,  A ,  R )  = inf ( C ,  A ,  R )
 
Theoreminfeq2 7015 Equality theorem for infimum. (Contributed by AV, 2-Sep-2020.)
 |-  ( B  =  C  -> inf ( A ,  B ,  R )  = inf ( A ,  C ,  R ) )
 
Theoreminfeq3 7016 Equality theorem for infimum. (Contributed by AV, 2-Sep-2020.)
 |-  ( R  =  S  -> inf ( A ,  B ,  R )  = inf ( A ,  B ,  S ) )
 
Theoreminfeq123d 7017 Equality deduction for infimum. (Contributed by AV, 2-Sep-2020.)
 |-  ( ph  ->  A  =  D )   &    |-  ( ph  ->  B  =  E )   &    |-  ( ph  ->  C  =  F )   =>    |-  ( ph  -> inf ( A ,  B ,  C )  = inf ( D ,  E ,  F ) )
 
Theoremnfinf 7018 Hypothesis builder for infimum. (Contributed by AV, 2-Sep-2020.)
 |-  F/_ x A   &    |-  F/_ x B   &    |-  F/_ x R   =>    |-  F/_ xinf ( A ,  B ,  R )
 
Theoremcnvinfex 7019* Two ways of expressing existence of an infimum (one in terms of converse). (Contributed by Jim Kingdon, 17-Dec-2021.)
 |-  ( ph  ->  E. x  e.  A  ( A. y  e.  B  -.  y R x  /\  A. y  e.  A  ( x R y  ->  E. z  e.  B  z R y ) ) )   =>    |-  ( ph  ->  E. x  e.  A  (
 A. y  e.  B  -.  x `' R y 
 /\  A. y  e.  A  ( y `' R x  ->  E. z  e.  B  y `' R z ) ) )
 
Theoremcnvti 7020* If a relation satisfies a condition corresponding to tightness of an apartness generated by an order, so does its converse. (Contributed by Jim Kingdon, 17-Dec-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   =>    |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u `' R v  /\  -.  v `' R u ) ) )
 
Theoremeqinfti 7021* Sufficient condition for an element to be equal to the infimum. (Contributed by Jim Kingdon, 16-Dec-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   =>    |-  ( ph  ->  ( ( C  e.  A  /\  A. y  e.  B  -.  y R C  /\  A. y  e.  A  ( C R y  ->  E. z  e.  B  z R y ) )  -> inf ( B ,  A ,  R )  =  C )
 )
 
Theoremeqinftid 7022* Sufficient condition for an element to be equal to the infimum. (Contributed by Jim Kingdon, 16-Dec-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   &    |-  ( ph  ->  C  e.  A )   &    |-  ( ( ph  /\  y  e.  B ) 
 ->  -.  y R C )   &    |-  ( ( ph  /\  (
 y  e.  A  /\  C R y ) ) 
 ->  E. z  e.  B  z R y )   =>    |-  ( ph  -> inf ( B ,  A ,  R )  =  C )
 
Theoreminfvalti 7023* Alternate expression for the infimum. (Contributed by Jim Kingdon, 17-Dec-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   &    |-  ( ph  ->  E. x  e.  A  ( A. y  e.  B  -.  y R x  /\  A. y  e.  A  ( x R y  ->  E. z  e.  B  z R y ) ) )   =>    |-  ( ph  -> inf ( B ,  A ,  R )  =  ( iota_ x  e.  A  ( A. y  e.  B  -.  y R x  /\  A. y  e.  A  ( x R y  ->  E. z  e.  B  z R y ) ) ) )
 
Theoreminfclti 7024* An infimum belongs to its base class (closure law). See also inflbti 7025 and infglbti 7026. (Contributed by Jim Kingdon, 17-Dec-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   &    |-  ( ph  ->  E. x  e.  A  ( A. y  e.  B  -.  y R x  /\  A. y  e.  A  ( x R y  ->  E. z  e.  B  z R y ) ) )   =>    |-  ( ph  -> inf ( B ,  A ,  R )  e.  A )
 
Theoreminflbti 7025* An infimum is a lower bound. See also infclti 7024 and infglbti 7026. (Contributed by Jim Kingdon, 18-Dec-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   &    |-  ( ph  ->  E. x  e.  A  ( A. y  e.  B  -.  y R x  /\  A. y  e.  A  ( x R y  ->  E. z  e.  B  z R y ) ) )   =>    |-  ( ph  ->  ( C  e.  B  ->  -.  C Rinf ( B ,  A ,  R ) ) )
 
Theoreminfglbti 7026* An infimum is the greatest lower bound. See also infclti 7024 and inflbti 7025. (Contributed by Jim Kingdon, 18-Dec-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   &    |-  ( ph  ->  E. x  e.  A  ( A. y  e.  B  -.  y R x  /\  A. y  e.  A  ( x R y  ->  E. z  e.  B  z R y ) ) )   =>    |-  ( ph  ->  ( ( C  e.  A  /\ inf ( B ,  A ,  R ) R C )  ->  E. z  e.  B  z R C ) )
 
Theoreminfnlbti 7027* A lower bound is not greater than the infimum. (Contributed by Jim Kingdon, 18-Dec-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   &    |-  ( ph  ->  E. x  e.  A  ( A. y  e.  B  -.  y R x  /\  A. y  e.  A  ( x R y  ->  E. z  e.  B  z R y ) ) )   =>    |-  ( ph  ->  ( ( C  e.  A  /\  A. z  e.  B  -.  z R C ) 
 ->  -. inf ( B ,  A ,  R ) R C ) )
 
Theoreminfminti 7028* The smallest element of a set is its infimum. Note that the converse is not true; the infimum might not be an element of the set considered. (Contributed by Jim Kingdon, 18-Dec-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   &    |-  ( ph  ->  C  e.  A )   &    |-  ( ph  ->  C  e.  B )   &    |-  (
 ( ph  /\  y  e.  B )  ->  -.  y R C )   =>    |-  ( ph  -> inf ( B ,  A ,  R )  =  C )
 
Theoreminfmoti 7029* Any class  B has at most one infimum in  A (where  R is interpreted as 'less than'). (Contributed by Jim Kingdon, 18-Dec-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   =>    |-  ( ph  ->  E* x  e.  A  ( A. y  e.  B  -.  y R x  /\  A. y  e.  A  ( x R y  ->  E. z  e.  B  z R y ) ) )
 
Theoreminfeuti 7030* An infimum is unique. (Contributed by Jim Kingdon, 19-Dec-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   &    |-  ( ph  ->  E. x  e.  A  ( A. y  e.  B  -.  y R x  /\  A. y  e.  A  ( x R y  ->  E. z  e.  B  z R y ) ) )   =>    |-  ( ph  ->  E! x  e.  A  (
 A. y  e.  B  -.  y R x  /\  A. y  e.  A  ( x R y  ->  E. z  e.  B  z R y ) ) )
 
Theoreminfsnti 7031* The infimum of a singleton. (Contributed by Jim Kingdon, 19-Dec-2021.)
 |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A )
 )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   &    |-  ( ph  ->  B  e.  A )   =>    |-  ( ph  -> inf ( { B } ,  A ,  R )  =  B )
 
Theoreminf00 7032 The infimum regarding an empty base set is always the empty set. (Contributed by AV, 4-Sep-2020.)
 |- inf
 ( B ,  (/) ,  R )  =  (/)
 
Theoreminfisoti 7033* Image of an infimum under an isomorphism. (Contributed by Jim Kingdon, 19-Dec-2021.)
 |-  ( ph  ->  F  Isom  R ,  S  ( A ,  B ) )   &    |-  ( ph  ->  C 
 C_  A )   &    |-  ( ph  ->  E. x  e.  A  ( A. y  e.  C  -.  y R x  /\  A. y  e.  A  ( x R y  ->  E. z  e.  C  z R y ) ) )   &    |-  ( ( ph  /\  ( u  e.  A  /\  v  e.  A ) )  ->  ( u  =  v  <->  ( -.  u R v  /\  -.  v R u ) ) )   =>    |-  ( ph  -> inf ( ( F " C ) ,  B ,  S )  =  ( F ` inf ( C ,  A ,  R ) ) )
 
Theoremsupex2g 7034 Existence of supremum. (Contributed by Jeff Madsen, 2-Sep-2009.)
 |-  ( A  e.  C  ->  sup ( B ,  A ,  R )  e.  _V )
 
Theoreminfex2g 7035 Existence of infimum. (Contributed by Jim Kingdon, 1-Oct-2024.)
 |-  ( A  e.  C  -> inf ( B ,  A ,  R )  e.  _V )
 
2.6.35  Ordinal isomorphism
 
Theoremordiso2 7036 Generalize ordiso 7037 to proper classes. (Contributed by Mario Carneiro, 24-Jun-2015.)
 |-  ( ( F  Isom  _E 
 ,  _E  ( A ,  B )  /\  Ord 
 A  /\  Ord  B ) 
 ->  A  =  B )
 
Theoremordiso 7037* Order-isomorphic ordinal numbers are equal. (Contributed by Jeff Hankins, 16-Oct-2009.) (Proof shortened by Mario Carneiro, 24-Jun-2015.)
 |-  ( ( A  e.  On  /\  B  e.  On )  ->  ( A  =  B 
 <-> 
 E. f  f  Isom  _E 
 ,  _E  ( A ,  B ) ) )
 
2.6.36  Disjoint union
 
2.6.36.1  Disjoint union
 
Syntaxcdju 7038 Extend class notation to include disjoint union of two classes.
 class  ( A B )
 
Definitiondf-dju 7039 Disjoint union of two classes. This is a way of creating a class which contains elements corresponding to each element of  A or  B, tagging each one with whether it came from  A or  B. (Contributed by Jim Kingdon, 20-Jun-2022.)
 |-  ( A B )  =  ( ( { (/) }  X.  A )  u.  ( { 1o }  X.  B ) )
 
Theoremdjueq12 7040 Equality theorem for disjoint union. (Contributed by Jim Kingdon, 23-Jun-2022.)
 |-  ( ( A  =  B  /\  C  =  D )  ->  ( A C )  =  ( B D ) )
 
Theoremdjueq1 7041 Equality theorem for disjoint union. (Contributed by Jim Kingdon, 23-Jun-2022.)
 |-  ( A  =  B  ->  ( A C )  =  ( B C )
 )
 
Theoremdjueq2 7042 Equality theorem for disjoint union. (Contributed by Jim Kingdon, 23-Jun-2022.)
 |-  ( A  =  B  ->  ( C A )  =  ( C B )
 )
 
Theoremnfdju 7043 Bound-variable hypothesis builder for disjoint union. (Contributed by Jim Kingdon, 23-Jun-2022.)
 |-  F/_ x A   &    |-  F/_ x B   =>    |-  F/_ x ( A B )
 
Theoremdjuex 7044 The disjoint union of sets is a set. See also the more precise djuss 7071. (Contributed by AV, 28-Jun-2022.)
 |-  ( ( A  e.  V  /\  B  e.  W )  ->  ( A B )  e.  _V )
 
Theoremdjuexb 7045 The disjoint union of two classes is a set iff both classes are sets. (Contributed by Jim Kingdon, 6-Sep-2023.)
 |-  ( ( A  e.  _V 
 /\  B  e.  _V ) 
 <->  ( A B )  e.  _V )
 
2.6.36.2  Left and right injections of a disjoint union

In this section, we define the left and right injections of a disjoint union and prove their main properties. These injections are restrictions of the "template" functions inl and inr, which appear in most applications in the form  (inl  |`  A ) and  (inr  |`  B ).

 
Syntaxcinl 7046 Extend class notation to include left injection of a disjoint union.
 class inl
 
Syntaxcinr 7047 Extend class notation to include right injection of a disjoint union.
 class inr
 
Definitiondf-inl 7048 Left injection of a disjoint union. (Contributed by Mario Carneiro, 21-Jun-2022.)
 |- inl 
 =  ( x  e. 
 _V  |->  <. (/) ,  x >. )
 
Definitiondf-inr 7049 Right injection of a disjoint union. (Contributed by Mario Carneiro, 21-Jun-2022.)
 |- inr 
 =  ( x  e. 
 _V  |->  <. 1o ,  x >. )
 
Theoremdjulclr 7050 Left closure of disjoint union. (Contributed by Jim Kingdon, 21-Jun-2022.) (Revised by BJ, 6-Jul-2022.)
 |-  ( C  e.  A  ->  ( (inl  |`  A ) `
  C )  e.  ( A B )
 )
 
Theoremdjurclr 7051 Right closure of disjoint union. (Contributed by Jim Kingdon, 21-Jun-2022.) (Revised by BJ, 6-Jul-2022.)
 |-  ( C  e.  B  ->  ( (inr  |`  B ) `
  C )  e.  ( A B )
 )
 
Theoremdjulcl 7052 Left closure of disjoint union. (Contributed by Jim Kingdon, 21-Jun-2022.)
 |-  ( C  e.  A  ->  (inl `  C )  e.  ( A B )
 )
 
Theoremdjurcl 7053 Right closure of disjoint union. (Contributed by Jim Kingdon, 21-Jun-2022.)
 |-  ( C  e.  B  ->  (inr `  C )  e.  ( A B )
 )
 
Theoremdjuf1olem 7054* Lemma for djulf1o 7059 and djurf1o 7060. (Contributed by BJ and Jim Kingdon, 4-Jul-2022.)
 |-  X  e.  _V   &    |-  F  =  ( x  e.  A  |->  <. X ,  x >. )   =>    |-  F : A -1-1-onto-> ( { X }  X.  A )
 
Theoremdjuf1olemr 7055* Lemma for djulf1or 7057 and djurf1or 7058. For a version of this lemma with  F defined on  A and no restriction in the conclusion, see djuf1olem 7054. (Contributed by BJ and Jim Kingdon, 4-Jul-2022.)
 |-  X  e.  _V   &    |-  F  =  ( x  e.  _V  |->  <. X ,  x >. )   =>    |-  ( F  |`  A ) : A -1-1-onto-> ( { X }  X.  A )
 
Theoremdjulclb 7056 Left biconditional closure of disjoint union. (Contributed by Jim Kingdon, 2-Jul-2022.)
 |-  ( C  e.  V  ->  ( C  e.  A  <->  (inl `  C )  e.  ( A B ) ) )
 
Theoremdjulf1or 7057 The left injection function on all sets is one to one and onto. (Contributed by BJ and Jim Kingdon, 22-Jun-2022.)
 |-  (inl  |`  A ) : A -1-1-onto-> ( { (/) }  X.  A )
 
Theoremdjurf1or 7058 The right injection function on all sets is one to one and onto. (Contributed by BJ and Jim Kingdon, 22-Jun-2022.)
 |-  (inr  |`  A ) : A -1-1-onto-> ( { 1o }  X.  A )
 
Theoremdjulf1o 7059 The left injection function on all sets is one to one and onto. (Contributed by Jim Kingdon, 22-Jun-2022.)
 |- inl : _V
 -1-1-onto-> ( { (/) }  X.  _V )
 
Theoremdjurf1o 7060 The right injection function on all sets is one to one and onto. (Contributed by Jim Kingdon, 22-Jun-2022.)
 |- inr : _V
 -1-1-onto-> ( { 1o }  X.  _V )
 
Theoreminresflem 7061* Lemma for inlresf1 7062 and inrresf1 7063. (Contributed by BJ, 4-Jul-2022.)
 |-  F : A -1-1-onto-> ( { X }  X.  A )   &    |-  ( x  e.  A  ->  ( F `  x )  e.  B )   =>    |-  F : A -1-1-> B
 
Theoreminlresf1 7062 The left injection restricted to the left class of a disjoint union is an injective function from the left class into the disjoint union. (Contributed by AV, 28-Jun-2022.)
 |-  (inl  |`  A ) : A -1-1-> ( A B )
 
Theoreminrresf1 7063 The right injection restricted to the right class of a disjoint union is an injective function from the right class into the disjoint union. (Contributed by AV, 28-Jun-2022.)
 |-  (inr  |`  B ) : B -1-1-> ( A B )
 
Theoremdjuinr 7064 The ranges of any left and right injections are disjoint. Remark: the extra generality offered by the two restrictions makes the theorem more readily usable (e.g., by djudom 7094 and djufun 7105) while the simpler statement  |-  ( ran inl  i^i 
ran inr )  =  (/) is easily recovered from it by substituting  _V for both  A and  B as done in casefun 7086). (Contributed by BJ and Jim Kingdon, 21-Jun-2022.)
 |-  ( ran  (inl  |`  A )  i^i  ran  (inr  |`  B ) )  =  (/)
 
Theoremdjuin 7065 The images of any classes under right and left injection produce disjoint sets. (Contributed by Jim Kingdon, 21-Jun-2022.) (Proof shortened by BJ, 9-Jul-2023.)
 |-  ( (inl " A )  i^i  (inr " B ) )  =  (/)
 
Theoreminl11 7066 Left injection is one-to-one. (Contributed by Jim Kingdon, 12-Jul-2023.)
 |-  ( ( A  e.  V  /\  B  e.  W )  ->  ( (inl `  A )  =  (inl `  B )  <->  A  =  B ) )
 
Theoremdjuunr 7067 The disjoint union of two classes is the union of the images of those two classes under right and left injection. (Contributed by Jim Kingdon, 22-Jun-2022.) (Proof shortened by BJ, 6-Jul-2022.)
 |-  ( ran  (inl  |`  A )  u.  ran  (inr  |`  B ) )  =  ( A B )
 
Theoremdjuun 7068 The disjoint union of two classes is the union of the images of those two classes under right and left injection. (Contributed by Jim Kingdon, 22-Jun-2022.) (Proof shortened by BJ, 9-Jul-2023.)
 |-  ( (inl " A )  u.  (inr " B ) )  =  ( A B )
 
Theoremeldju 7069* Element of a disjoint union. (Contributed by BJ and Jim Kingdon, 23-Jun-2022.)
 |-  ( C  e.  ( A B )  <->  ( E. x  e.  A  C  =  ( (inl  |`  A ) `  x )  \/  E. x  e.  B  C  =  ( (inr  |`  B ) `  x ) ) )
 
Theoremdjur 7070* A member of a disjoint union can be mapped from one of the classes which produced it. (Contributed by Jim Kingdon, 23-Jun-2022.) Upgrade implication to biconditional and shorten proof. (Revised by BJ, 14-Jul-2023.)
 |-  ( C  e.  ( A B )  <->  ( E. x  e.  A  C  =  (inl `  x )  \/  E. x  e.  B  C  =  (inr `  x )
 ) )
 
2.6.36.3  Universal property of the disjoint union
 
Theoremdjuss 7071 A disjoint union is a subset of a Cartesian product. (Contributed by AV, 25-Jun-2022.)
 |-  ( A B )  C_  ( { (/) ,  1o }  X.  ( A  u.  B ) )
 
Theoremeldju1st 7072 The first component of an element of a disjoint union is either  (/) or  1o. (Contributed by AV, 26-Jun-2022.)
 |-  ( X  e.  ( A B )  ->  (
 ( 1st `  X )  =  (/)  \/  ( 1st `  X )  =  1o ) )
 
Theoremeldju2ndl 7073 The second component of an element of a disjoint union is an element of the left class of the disjoint union if its first component is the empty set. (Contributed by AV, 26-Jun-2022.)
 |-  ( ( X  e.  ( A B )  /\  ( 1st `  X )  =  (/) )  ->  ( 2nd `  X )  e.  A )
 
Theoremeldju2ndr 7074 The second component of an element of a disjoint union is an element of the right class of the disjoint union if its first component is not the empty set. (Contributed by AV, 26-Jun-2022.)
 |-  ( ( X  e.  ( A B )  /\  ( 1st `  X )  =/= 
 (/) )  ->  ( 2nd `  X )  e.  B )
 
Theorem1stinl 7075 The first component of the value of a left injection is the empty set. (Contributed by AV, 27-Jun-2022.)
 |-  ( X  e.  V  ->  ( 1st `  (inl `  X ) )  =  (/) )
 
Theorem2ndinl 7076 The second component of the value of a left injection is its argument. (Contributed by AV, 27-Jun-2022.)
 |-  ( X  e.  V  ->  ( 2nd `  (inl `  X ) )  =  X )
 
Theorem1stinr 7077 The first component of the value of a right injection is  1o. (Contributed by AV, 27-Jun-2022.)
 |-  ( X  e.  V  ->  ( 1st `  (inr `  X ) )  =  1o )
 
Theorem2ndinr 7078 The second component of the value of a right injection is its argument. (Contributed by AV, 27-Jun-2022.)
 |-  ( X  e.  V  ->  ( 2nd `  (inr `  X ) )  =  X )
 
Theoremdjune 7079 Left and right injection never produce equal values. (Contributed by Jim Kingdon, 2-Jul-2022.)
 |-  ( ( A  e.  V  /\  B  e.  W )  ->  (inl `  A )  =/=  (inr `  B ) )
 
Theoremupdjudhf 7080* The mapping of an element of the disjoint union to the value of the corresponding function is a function. (Contributed by AV, 26-Jun-2022.)
 |-  ( ph  ->  F : A --> C )   &    |-  ( ph  ->  G : B --> C )   &    |-  H  =  ( x  e.  ( A B )  |->  if (
 ( 1st `  x )  =  (/) ,  ( F `
  ( 2nd `  x ) ) ,  ( G `  ( 2nd `  x ) ) ) )   =>    |-  ( ph  ->  H :
 ( A B ) --> C )
 
Theoremupdjudhcoinlf 7081* The composition of the mapping of an element of the disjoint union to the value of the corresponding function and the left injection equals the first function. (Contributed by AV, 27-Jun-2022.)
 |-  ( ph  ->  F : A --> C )   &    |-  ( ph  ->  G : B --> C )   &    |-  H  =  ( x  e.  ( A B )  |->  if (
 ( 1st `  x )  =  (/) ,  ( F `
  ( 2nd `  x ) ) ,  ( G `  ( 2nd `  x ) ) ) )   =>    |-  ( ph  ->  ( H  o.  (inl  |`  A ) )  =  F )
 
Theoremupdjudhcoinrg 7082* The composition of the mapping of an element of the disjoint union to the value of the corresponding function and the right injection equals the second function. (Contributed by AV, 27-Jun-2022.)
 |-  ( ph  ->  F : A --> C )   &    |-  ( ph  ->  G : B --> C )   &    |-  H  =  ( x  e.  ( A B )  |->  if (
 ( 1st `  x )  =  (/) ,  ( F `
  ( 2nd `  x ) ) ,  ( G `  ( 2nd `  x ) ) ) )   =>    |-  ( ph  ->  ( H  o.  (inr  |`  B ) )  =  G )
 
Theoremupdjud 7083* Universal property of the disjoint union. (Proposed by BJ, 25-Jun-2022.) (Contributed by AV, 28-Jun-2022.)
 |-  ( ph  ->  F : A --> C )   &    |-  ( ph  ->  G : B --> C )   &    |-  ( ph  ->  A  e.  V )   &    |-  ( ph  ->  B  e.  W )   =>    |-  ( ph  ->  E! h ( h :
 ( A B ) --> C  /\  ( h  o.  (inl  |`  A ) )  =  F  /\  ( h  o.  (inr  |`  B ) )  =  G ) )
 
Syntaxcdjucase 7084 Syntax for the "case" construction.
 class case ( R ,  S )
 
Definitiondf-case 7085 The "case" construction: if  F : A --> X and  G : B --> X are functions, then case ( F ,  G
) : ( A B ) --> X is the natural function obtained by a definition by cases, hence the name. It is the unique function whose existence is asserted by the universal property of disjoint unions updjud 7083. The definition is adapted to make sense also for binary relations (where the universal property also holds). (Contributed by MC and BJ, 10-Jul-2022.)
 |- case
 ( R ,  S )  =  ( ( R  o.  `'inl )  u.  ( S  o.  `'inr ) )
 
Theoremcasefun 7086 The "case" construction of two functions is a function. (Contributed by BJ, 10-Jul-2022.)
 |-  ( ph  ->  Fun  F )   &    |-  ( ph  ->  Fun  G )   =>    |-  ( ph  ->  Fun case ( F ,  G ) )
 
Theoremcasedm 7087 The domain of the "case" construction is the disjoint union of the domains. TODO (although less important):  |-  ran case ( F ,  G )  =  ( ran  F  u.  ran  G ). (Contributed by BJ, 10-Jul-2022.)
 |- 
 dom case ( F ,  G )  =  ( dom  F dom  G )
 
Theoremcaserel 7088 The "case" construction of two relations is a relation, with bounds on its domain and codomain. Typically, the "case" construction is used when both relations have a common codomain. (Contributed by BJ, 10-Jul-2022.)
 |- case
 ( R ,  S )  C_  ( ( dom 
 R dom  S )  X.  ( ran  R  u.  ran  S ) )
 
Theoremcasef 7089 The "case" construction of two functions is a function on the disjoint union of their domains. (Contributed by BJ, 10-Jul-2022.)
 |-  ( ph  ->  F : A --> X )   &    |-  ( ph  ->  G : B --> X )   =>    |-  ( ph  -> case ( F ,  G ) : ( A B ) --> X )
 
Theoremcaseinj 7090 The "case" construction of two injective relations with disjoint ranges is an injective relation. (Contributed by BJ, 10-Jul-2022.)
 |-  ( ph  ->  Fun  `' R )   &    |-  ( ph  ->  Fun  `' S )   &    |-  ( ph  ->  ( ran  R  i^i  ran  S )  =  (/) )   =>    |-  ( ph  ->  Fun  `'case ( R ,  S ) )
 
Theoremcasef1 7091 The "case" construction of two injective functions with disjoint ranges is an injective function. (Contributed by BJ, 10-Jul-2022.)
 |-  ( ph  ->  F : A -1-1-> X )   &    |-  ( ph  ->  G : B -1-1-> X )   &    |-  ( ph  ->  ( ran  F  i^i  ran  G )  =  (/) )   =>    |-  ( ph  -> case ( F ,  G ) : ( A B ) -1-1-> X )
 
Theoremcaseinl 7092 Applying the "case" construction to a left injection. (Contributed by Jim Kingdon, 15-Mar-2023.)
 |-  ( ph  ->  F  Fn  B )   &    |-  ( ph  ->  Fun 
 G )   &    |-  ( ph  ->  A  e.  B )   =>    |-  ( ph  ->  (case ( F ,  G ) `  (inl `  A ) )  =  ( F `  A ) )
 
Theoremcaseinr 7093 Applying the "case" construction to a right injection. (Contributed by Jim Kingdon, 12-Jul-2023.)
 |-  ( ph  ->  Fun  F )   &    |-  ( ph  ->  G  Fn  B )   &    |-  ( ph  ->  A  e.  B )   =>    |-  ( ph  ->  (case ( F ,  G ) `  (inr `  A ) )  =  ( G `  A ) )
 
2.6.36.4  Dominance and equinumerosity properties of disjoint union
 
Theoremdjudom 7094 Dominance law for disjoint union. (Contributed by Jim Kingdon, 25-Jul-2022.)
 |-  ( ( A  ~<_  B  /\  C 
 ~<_  D )  ->  ( A C )  ~<_  ( B D ) )
 
Theoremomp1eomlem 7095* Lemma for omp1eom 7096. (Contributed by Jim Kingdon, 11-Jul-2023.)
 |-  F  =  ( x  e.  om  |->  if ( x  =  (/) ,  (inr `  x ) ,  (inl ` 
 U. x ) ) )   &    |-  S  =  ( x  e.  om  |->  suc 
 x )   &    |-  G  = case ( S ,  (  _I  |` 
 1o ) )   =>    |-  F : om -1-1-onto-> ( om 1o )
 
Theoremomp1eom 7096 Adding one to  om. (Contributed by Jim Kingdon, 10-Jul-2023.)
 |-  ( om 1o )  ~~  om
 
Theoremendjusym 7097 Reversing right and left operands of a disjoint union produces an equinumerous result. (Contributed by Jim Kingdon, 10-Jul-2023.)
 |-  ( ( A  e.  V  /\  B  e.  W )  ->  ( A B ) 
 ~~  ( B A ) )
 
Theoremeninl 7098 Equinumerosity of a set and its image under left injection. (Contributed by Jim Kingdon, 30-Jul-2023.)
 |-  ( A  e.  V  ->  (inl " A )  ~~  A )
 
Theoremeninr 7099 Equinumerosity of a set and its image under right injection. (Contributed by Jim Kingdon, 30-Jul-2023.)
 |-  ( A  e.  V  ->  (inr " A )  ~~  A )
 
Theoremdifinfsnlem 7100* Lemma for difinfsn 7101. The case where we need to swap  B and  (inr `  (/) ) in building the mapping  G. (Contributed by Jim Kingdon, 9-Aug-2023.)
 |-  ( ph  ->  A. x  e.  A  A. y  e.  A DECID  x  =  y )   &    |-  ( ph  ->  B  e.  A )   &    |-  ( ph  ->  F : ( om 1o ) -1-1-> A )   &    |-  ( ph  ->  ( F `  (inr `  (/) ) )  =/=  B )   &    |-  G  =  ( n  e.  om  |->  if (
 ( F `  (inl `  n ) )  =  B ,  ( F `
  (inr `  (/) ) ) ,  ( F `  (inl `  n ) ) ) )   =>    |-  ( ph  ->  G : om -1-1-> ( A  \  { B } ) )
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