Theorem List for New Foundations Explorer - 4701-4800   *Has distinct variable
 group(s)
| Type | Label | Description | 
| Statement | 
|   | 
| Theorem | opelopabga 4701* | 
The law of concretion.  Theorem 9.5 of [Quine] p.
61.  (Contributed by
       Mario Carneiro, 19-Dec-2013.)
 | 
                                                                
                      | 
|   | 
| Theorem | brabga 4702* | 
The law of concretion for a binary relation.  (Contributed by Mario
         Carneiro, 19-Dec-2013.)
 | 
                                         
        
                                            | 
|   | 
| Theorem | opelopab2a 4703* | 
Ordered pair membership in an ordered pair class abstraction.
       (Contributed by Mario Carneiro, 19-Dec-2013.)
 | 
                                                                
                
                          | 
|   | 
| Theorem | opelopaba 4704* | 
The law of concretion.  Theorem 9.5 of [Quine] p.
61.  (Contributed by
       Mario Carneiro, 19-Dec-2013.)
 | 
                                 
                                                             | 
|   | 
| Theorem | braba 4705* | 
The law of concretion for a binary relation.  (Contributed by NM,
         19-Dec-2013.)
 | 
                                 
                                    
        
                        | 
|   | 
| Theorem | opelopabg 4706* | 
The law of concretion.  Theorem 9.5 of [Quine] p.
61.  (Contributed by
       NM, 28-May-1995.)  (Revised by set.mm contributors, 19-Dec-2013.)
 | 
                                                                                
                      | 
|   | 
| Theorem | brabg 4707* | 
The law of concretion for a binary relation.  (Contributed by NM,
         16-Aug-1999.)  (Revised by set.mm contributors, 19-Dec-2013.)
 | 
                                                         
        
                                            | 
|   | 
| Theorem | opelopab2 4708* | 
Ordered pair membership in an ordered pair class abstraction.
       (Contributed by NM, 14-Oct-2007.)  (Revised by set.mm contributors,
       19-Dec-2013.)
 | 
                                                                                
                
                          | 
|   | 
| Theorem | opelopab 4709* | 
The law of concretion.  Theorem 9.5 of [Quine] p.
61.  (Contributed by
       NM, 16-May-1995.)
 | 
                                  
                          
                                                  | 
|   | 
| Theorem | brab 4710* | 
The law of concretion for a binary relation.  (Contributed by NM,
         16-Aug-1999.)
 | 
                                  
                          
                                                         | 
|   | 
| Theorem | opelopabaf 4711* | 
The law of concretion.  Theorem 9.5 of [Quine] p.
61.  This version of
       opelopab 4709 uses bound-variable hypotheses in place of
distinct variable
       conditions."  (Contributed by Mario Carneiro, 19-Dec-2013.)  (Proof
       shortened by Mario Carneiro, 18-Nov-2016.)
 | 
                                                                                                                      | 
|   | 
| Theorem | opelopabf 4712* | 
The law of concretion.  Theorem 9.5 of [Quine] p.
61.  This version of
       opelopab 4709 uses bound-variable hypotheses in place of
distinct variable
       conditions."  (Contributed by NM, 19-Dec-2008.)
 | 
                                                                                                                                      | 
|   | 
| Theorem | ssopab2 4713 | 
Equivalence of ordered pair abstraction subclass and implication.
       (Contributed by NM, 27-Dec-1996.)  (Revised by Mario Carneiro,
       19-May-2013.)
 | 
                        
                      | 
|   | 
| Theorem | ssopab2b 4714 | 
Equivalence of ordered pair abstraction subclass and implication.
     (Contributed by NM, 27-Dec-1996.)  (Proof shortened by Mario Carneiro,
     18-Nov-2016.)
 | 
          
                                    | 
|   | 
| Theorem | ssopab2i 4715 | 
Inference of ordered pair abstraction subclass from implication.
       (Contributed by NM, 5-Apr-1995.)
 | 
                                              | 
|   | 
| Theorem | ssopab2dv 4716* | 
Inference of ordered pair abstraction subclass from implication.
       (Contributed by NM, 19-Jan-2014.)  (Revised by Mario Carneiro,
       24-Jun-2014.)
 | 
                                                          | 
|   | 
| Theorem | opabn0 4717 | 
Nonempty ordered pair class abstraction.  (Contributed by NM,
       10-Oct-2007.)
 | 
          
                   | 
|   | 
| 2.3.5  Set construction functions
 | 
|   | 
| Syntax | c1st 4718 | 
Extend the definition of a class to include the first member an ordered
     pair function.
 | 
    | 
|   | 
| Syntax | cswap 4719 | 
Extend the definition of a class to include the swap function.
 | 
   Swap
  | 
|   | 
| Syntax | csset 4720 | 
Extend the definition of a class to include the subset relationship.
 | 
   S  | 
|   | 
| Syntax | csi 4721 | 
Extend the definition of a class to include the singleton image.
 | 
   SI   | 
|   | 
| Syntax | ccom 4722 | 
Extend the definition of a class to include the composition of two
     classes.
 | 
    
      | 
|   | 
| Syntax | cima 4723 | 
Extend the definition of a class to include the image of one class under
     another.
 | 
        | 
|   | 
| Definition | df-1st 4724* | 
Define a function that extracts the first member, or abscissa, of an
       ordered pair.  (Contributed by SF, 5-Jan-2015.)
 | 
             
         
         | 
|   | 
| Definition | df-swap 4725* | 
Define a function that swaps the two elements of an ordered pair.
       (Contributed by SF, 5-Jan-2015.)
 | 
   Swap                             
                | 
|   | 
| Definition | df-sset 4726* | 
Define a relationship that holds between subsets.  (Contributed by SF,
       5-Jan-2015.)
 | 
   S                 
    | 
|   | 
| Definition | df-co 4727* | 
Define the composition of two classes.  (Contributed by SF,
       5-Jan-2015.)
 | 
           
        
                  | 
|   | 
| Definition | df-ima 4728* | 
Define the image of one class under another.  (Contributed by SF,
       5-Jan-2015.)
 | 
         
                  | 
|   | 
| Definition | df-si 4729* | 
Define the singleton image of a class.  (Contributed by SF,
       5-Jan-2015.)
 | 
   SI                                              | 
|   | 
| Theorem | el1st 4730* | 
Membership in  . 
(Contributed by SF, 5-Jan-2015.)
 | 
                                 | 
|   | 
| Theorem | br1stg 4731 | 
The binary relationship over the   function.  (Contributed by SF,
       5-Jan-2015.)
 | 
                                    
     | 
|   | 
| Theorem | setconslem1 4732* | 
Lemma for the set construction theorems.  (Contributed by SF,
       6-Jan-2015.)
 | 
                                       
     Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k           
        
  Phi    | 
|   | 
| Theorem | setconslem2 4733* | 
Lemma for the set construction theorems.  (Contributed by SF,
       6-Jan-2015.)
 | 
                                       
      Ins2k
 Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c      
        
  
 Phi      0c    | 
|   | 
| Theorem | setconslem3 4734 | 
Lemma for set construction functions.  Set up a mapping between
       Kuratowski and Quine ordered pairs.  (Contributed by SF, 7-Jan-2015.)
 | 
                                                            
   ∼    Ins3k SIk SIk Sk   Ins2k   Ins3k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins2k
    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c    k 1  1  1  1 1c                | 
|   | 
| Theorem | setconslem4 4735* | 
Lemma for set construction functions.  Create a mapping between the two
       types of ordered pair abstractions.  (Contributed by SF, 7-Jan-2015.)
 | 
  ⋃1⋃1       k     k   
    k
 ∼    Ins3k SIk SIk Sk   Ins2k   Ins3k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins2k
    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c    k 1  1  1  1 1c   k                           | 
|   | 
| Theorem | setconslem5 4736 | 
Lemma for set construction theorems.  The big expression in the middle of
     setconslem4 4735 forms a set.  (Contributed by SF,
7-Jan-2015.)
 | 
  ∼   
 Ins3k SIk SIk Sk   Ins2k   Ins3k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins2k
    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c    k 1  1  1  1 1c      | 
|   | 
| Theorem | setconslem6 4737* | 
Lemma for the set construction functions.  Invert the expression from
       setconslem4 4735.  (Contributed by SF, 7-Jan-2015.)
 | 
        k     k       ∼    Ins3k SIk SIk Sk   Ins2k   Ins3k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins2k
    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c    k 1  1  1  1 1c   k 1  1                                          | 
|   | 
| Theorem | setconslem7 4738 | 
Lemma for the set construction theorems.  Reorganized version of
       setconslem3 4734.  (Contributed by SF, 4-Feb-2015.)
 | 
                                                            
   ∼    Ins2k Ins3k Sk     Ins2k Ins2k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins3k
 SIk SIk    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c    k 1  1  1  1 1c                | 
|   | 
| Theorem | df1st2 4739 | 
Express the  
function via the set construction functions.
       (Contributed by SF, 4-Feb-2015.)
 | 
      ⋃1⋃1       k     k   
    k
 ∼    Ins3k SIk SIk Sk   Ins2k   Ins3k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins2k
    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c    k 1  1  1  1 1c   k  ∼    Ins2k Ins3k Sk     Ins2k Ins2k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins3k
 SIk SIk    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c    k 1  1  1  1 1c  k 1 1c   | 
|   | 
| Theorem | 1stex 4740 | 
The   function is a
set.  (Contributed by SF, 6-Jan-2015.)
 | 
        | 
|   | 
| Theorem | elswap 4741* | 
Membership in the  Swap  function.  (Contributed
by SF,
       6-Jan-2015.)
 | 
       
 Swap                               | 
|   | 
| Theorem | dfswap2 4742 | 
Express the  Swap  function via set construction
operators.
       (Contributed by SF, 6-Jan-2015.)
 | 
   Swap       ∼    Ins2k Ins2k Sk       Ins2k   Ins2k Ins3k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins3k
 SIk SIk    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c     Ins3k SIk SIk SIk SIk SIk Imagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k 1  1  1  1  1  1 1c       Ins2k   Ins3k SIk SIk   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins2k
 Ins3k    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c     Ins3k SIk SIk SIk SIk SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1  1  1  1  1 1c    k 1  1  1  1 1c  k 1 1c  k   | 
|   | 
| Theorem | swapex 4743 | 
The  Swap  function is a set.  (Contributed by SF,
6-Jan-2015.)
 | 
   Swap      | 
|   | 
| Theorem | dfsset2 4744 | 
Express the  S  relationship via the set
construction functors.
       (Contributed by SF, 7-Jan-2015.)
 | 
   S   
 ⋃1⋃1       k     k   
    k
 ∼    Ins3k SIk SIk Sk   Ins2k   Ins3k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins2k
    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c    k 1  1  1  1 1c   k Sk   | 
|   | 
| Theorem | ssetex 4745 | 
The subset relationship is a set.  (Contributed by SF, 6-Jan-2015.)
 | 
   S      | 
|   | 
| Theorem | dfima2 4746 | 
Express the image functor in terms of the set construction functions.
       (Contributed by SF, 7-Jan-2015.)
 | 
         
        k     k       ∼    Ins3k SIk SIk Sk   Ins2k   Ins3k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins2k
    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c    k 1  1  1  1 1c   k 1  1    k   | 
|   | 
| Theorem | imaexg 4747 | 
The image of a set under a set is a set.  (Contributed by SF,
     7-Jan-2015.)
 | 
                          
      | 
|   | 
| Theorem | imaex 4748 | 
The image of a set under a set is a set.  (Contributed by SF,
       7-Jan-2015.)
 | 
                                        | 
|   | 
| Theorem | dfco1 4749 | 
Express Quine composition via Kuratowski composition.  (Contributed by
       SF, 7-Jan-2015.)
 | 
           
 ⋃1⋃1       k     k   
    k
 ∼    Ins3k SIk SIk Sk   Ins2k   Ins3k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins2k
    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c    k 1  1  1  1 1c   k       k     k       ∼    Ins3k SIk SIk Sk   Ins2k   Ins3k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins2k
    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c    k 1  1  1  1 1c   k 1  1     k       k     k       ∼    Ins3k SIk SIk Sk   Ins2k   Ins3k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins2k
    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c    k 1  1  1  1 1c   k 1  1      | 
|   | 
| Theorem | coexg 4750 | 
The composition of two sets is a set.  (Contributed by SF, 7-Jan-2015.)
 | 
                            
      | 
|   | 
| Theorem | coex 4751 | 
The composition of two sets is a set.  (Contributed by SF,
       7-Jan-2015.)
 | 
                                          | 
|   | 
| Theorem | dfsi2 4752 | 
Express singleton image in terms of the Kuratowski singleton image.
       (Contributed by SF, 7-Jan-2015.)
 | 
   SI    
 ⋃1⋃1       k     k   
    k
 ∼    Ins3k SIk SIk Sk   Ins2k   Ins3k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins2k
    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c    k 1  1  1  1 1c   k SIk       k     k       ∼    Ins3k SIk SIk Sk   Ins2k   Ins3k   Sk  k SIk  kImagek  Imagek   Ins3k
 ∼    Ins3k Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k         Ins2k
    Ins2k Sk   Ins3k SIk ∼    Ins2k Sk   Ins3k    kImagek  Imagek  
 Ins3k ∼    Ins3k
 Sk   Ins2k Sk   k 1  1 1c       Ins2k Ins2k Sk     Ins2k Ins3k Sk   Ins3k SIk SIk Sk    k 1  1  1  1 1c   k 1  1 1c      Nn  k          k     ∼ Nn  k       k Sk        0c    k      k 1  1 1c   k 1  1 1c    k 1  1  1  1 1c   k 1  1     | 
|   | 
| Theorem | siexg 4753 | 
The singleton image of a set is a set.  (Contributed by SF,
     7-Jan-2015.)
 | 
            SI        | 
|   | 
| Theorem | siex 4754 | 
The singleton image of a set is a set.  (Contributed by SF,
       7-Jan-2015.)
 | 
                 SI       | 
|   | 
| Theorem | elima 4755* | 
Membership in an image.  Theorem 34 of [Suppes]
p. 65.  (Contributed by
       SF, 19-Apr-2004.)
 | 
                           | 
|   | 
| Theorem | elima2 4756* | 
Membership in an image.  Theorem 34 of [Suppes]
p. 65.  (Contributed by
       SF, 11-Aug-2004.)
 | 
                   
             | 
|   | 
| Theorem | elima3 4757* | 
Membership in an image.  Theorem 34 of [Suppes]
p. 65.  (Contributed by
       SF, 14-Aug-1994.)
 | 
                   
                    | 
|   | 
| Theorem | brssetg 4758 | 
Binary relationship form of the subset relationship.  (Contributed by
       SF, 11-Feb-2015.)
 | 
                        S
             | 
|   | 
| Theorem | brsset 4759 | 
Binary relationship form of the subset relationship.  (Contributed by
       SF, 11-Feb-2015.)
 | 
                                 S            | 
|   | 
| Theorem | brssetsn 4760 | 
Set membership in terms of the subset relationship.  (Contributed by SF,
       11-Feb-2015.)
 | 
                                   S            | 
|   | 
| Theorem | opelssetsn 4761 | 
Set membership in terms of the subset relationship.  (Contributed by SF,
       11-Feb-2015.)
 | 
                                           S           | 
|   | 
| Theorem | brsi 4762* | 
Binary relationship over a singleton image.  (Contributed by SF,
       11-Feb-2015.)
 | 
     SI                                     | 
|   | 
| 2.3.6  Epsilon and identity
 relations
 | 
|   | 
| Syntax | cep 4763 | 
Extend class notation to include the epsilon relation.
 | 
    | 
|   | 
| Syntax | cid 4764 | 
Extend the definition of a class to include identity relation.
 | 
    | 
|   | 
| Definition | df-eprel 4765* | 
Define the epsilon relation.  Similar to Definition 6.22 of
       [TakeutiZaring] p. 30. 
(Contributed by SF, 5-Jan-2015.)
 | 
             
          | 
|   | 
| Theorem | epelc 4766 | 
The epsilon relation and the membership relation are the same.
       (Contributed by NM, 13-Aug-1995.)
 | 
                                | 
|   | 
| Theorem | epel 4767 | 
The epsilon relation and the membership relation are the same.
     (Contributed by NM, 13-Aug-1995.)
 | 
                  | 
|   | 
| Definition | df-id 4768* | 
Define the identity relation.  Definition 9.15 of [Quine] p. 64.
       (Contributed by SF, 5-Jan-2015.)
 | 
             
          | 
|   | 
| Theorem | dfid3 4769 | 
A stronger version of df-id 4768 that doesn't require   and   to be
       distinct.  Ordinarily, we wouldn't use this as a definition, since
       non-distinct dummy variables would make soundness verification more
       difficult (as the proof here shows).  The proof can be instructive in
       showing how distinct variable requirements may be eliminated, a task
       that is not necessarily obvious.  (Contributed by NM, 5-Feb-2008.)
       (Revised by Mario Carneiro, 18-Nov-2016.)
 | 
             
          | 
|   | 
| Theorem | dfid2 4770 | 
Alternate definition of the identity relation.  (Contributed by NM,
     15-Mar-2007.)
 | 
             
          | 
|   | 
| 2.3.7  Functions and relations
 | 
|   | 
| Syntax | cxp 4771 | 
Extend the definition of a class to include the cross product.
 | 
    
      | 
|   | 
| Syntax | ccnv 4772 | 
Extend the definition of a class to include the converse of a class.
 | 
     | 
|   | 
| Syntax | cdm 4773 | 
Extend the definition of a class to include the domain of a class.
 | 
      | 
|   | 
| Syntax | crn 4774 | 
Extend the definition of a class to include the range of a class.
 | 
      | 
|   | 
| Syntax | cres 4775 | 
Extend the definition of a class to include the restriction of a class.
     (Read:  The restriction of   to  .)
 | 
    
      | 
|   | 
| Syntax | wfun 4776 | 
Extend the definition of a wff to include the function predicate.  (Read:
       is a function.)
 | 
      | 
|   | 
| Syntax | wfn 4777 | 
Extend the definition of a wff to include the function predicate with a
     domain.  (Read:  
is a function on  .)
 | 
        | 
|   | 
| Syntax | wf 4778 | 
Extend the definition of a wff to include the function predicate with
     domain and codomain.  (Read:   maps   into  .)
 | 
        | 
|   | 
| Syntax | wf1 4779 | 
Extend the definition of a wff to include one-to-one functions.  (Read:
       maps   one-to-one into  .)  The notation
("1-1" above the
     arrow) is from Definition 6.15(5) of [TakeutiZaring] p. 27.
 | 
        | 
|   | 
| Syntax | wfo 4780 | 
Extend the definition of a wff to include onto functions.  (Read:  
     maps   onto  .)  The notation
("onto" below the arrow) is from
     Definition 6.15(4) of [TakeutiZaring] p. 27.
 | 
        | 
|   | 
| Syntax | wf1o 4781 | 
Extend the definition of a wff to include one-to-one onto functions.
     (Read:   maps
  one-to-one onto  .)  The notation
("1-1"
     above the arrow and "onto" below the arrow) is from Definition
6.15(6) of
     [TakeutiZaring] p. 27.
 | 
        | 
|   | 
| Syntax | cfv 4782 | 
Extend the definition of a class to include the value of a function.
     (Read:  The value of   at  , or
"  of  .")
 | 
        | 
|   | 
| Syntax | wiso 4783 | 
Extend the definition of a wff to include the isomorphism property.
     (Read:   is an
 ,   isomorphism of   onto  .)
 | 
     
             | 
|   | 
| Syntax | c2nd 4784 | 
Extend the definition of a class to include the second function.
 | 
    | 
|   | 
| Definition | df-xp 4785* | 
Define the cross product of two classes.  Definition 9.11 of [Quine]
       p. 64.  (Contributed by SF, 5-Jan-2015.)
 | 
           
        
                    | 
|   | 
| Definition | df-cnv 4786* | 
Define the converse of a class.  Definition 9.12 of [Quine] p. 64.  We
       use Quine's breve accent (smile) notation.  Like Quine, we use it as a
       prefix, which eliminates the need for parentheses.  Many authors use the
       postfix superscript "to the minus one."  "Converse"
is Quine's
       terminology; some authors call it "inverse," especially when
the
       argument is a function.  (Contributed by SF, 5-Jan-2015.)
 | 
                      | 
|   | 
| Definition | df-rn 4787 | 
Define the range of a class.  The notation "  " is used by
       Enderton; other authors sometimes use script R or script W. (Contributed
       by SF, 5-Jan-2015.)
 | 
              | 
|   | 
| Definition | df-dm 4788 | 
Define the domain of a class.  The notation "  " is used by
       Enderton; other authors sometimes use script D. (Contributed by SF,
       5-Jan-2015.)
 | 
             | 
|   | 
| Definition | df-res 4789 | 
Define the restriction of a class.  Definition 6.6(1) of [TakeutiZaring]
       p. 24.  (Contributed by SF, 5-Jan-2015.)
 | 
                   
       | 
|   | 
| Definition | df-fun 4790 | 
Define a function.  Definition 10.1 of [Quine] p.
65.  For alternate
       definitions, see dffun2 5120, dffun3 5121, dffun4 5122, dffun5 5123, dffun6 5125,
       dffun7 5134, dffun8 5135, and dffun9 5136.  (Contributed by SF, 5-Jan-2015.)
       (Revised by Scott Fenton, 14-Apr-2021.)
 | 
                        | 
|   | 
| Definition | df-fn 4791 | 
Define a function with domain.  Definition 6.15(1) of [TakeutiZaring]
       p. 27.  For alternate definitions, see dffn2 5225, dffn3 5230, dffn4 5276, and
       dffn5 5364.  (Contributed by SF, 5-Jan-2015.)
 | 
                            | 
|   | 
| Definition | df-f 4792 | 
Define a function (mapping) with domain and codomain.  Definition
       6.15(3) of [TakeutiZaring] p. 27. 
For alternate definitions, see
       dff2 5420, dff3 5421, and dff4 5422.
(Contributed by SF, 5-Jan-2015.)
 | 
                         
     | 
|   | 
| Definition | df-f1 4793 | 
Define a one-to-one function.  For equivalent definitions see dff12 5258
       and dff13 5472.  Compare Definition 6.15(5) of [TakeutiZaring] p. 27.  We
       use their notation ("1-1" above the arrow).  (Contributed by
SF,
       5-Jan-2015.)
 | 
                           | 
|   | 
| Definition | df-fo 4794 | 
Define an onto function.  Definition 6.15(4) of [TakeutiZaring] p. 27.
       We use their notation ("onto" under the arrow).  For alternate
       definitions, see dffo2 5274, dffo3 5423, dffo4 5424, and dffo5 5425.
       (Contributed by SF, 5-Jan-2015.)
 | 
                              | 
|   | 
| Definition | df-f1o 4795 | 
Define a one-to-one onto function.  For equivalent definitions see
       dff1o2 5292, dff1o3 5293, dff1o4 5295, and dff1o5 5296.  Compare Definition
       6.15(6) of [TakeutiZaring] p. 27. 
We use their notation ("1-1" above
       the arrow and "onto" below the arrow).  (Contributed by SF,
       5-Jan-2015.)
 | 
                            | 
|   | 
| Definition | df-fv 4796* | 
Define the value of a function.  (Contributed by SF, 5-Jan-2015.)
 | 
         
         | 
|   | 
| Definition | df-iso 4797* | 
Define the isomorphism predicate.  We read this as "  is an  ,
         isomorphism
of   onto  ."  Normally,   and   are
       ordering relations on   and  
respectively.  Definition 6.28 of
       [TakeutiZaring] p. 32, whose
notation is the same as ours except that
         and   are subscripts. 
(Contributed by SF, 5-Jan-2015.)
 | 
                  
  
                                              | 
|   | 
| Definition | df-2nd 4798* | 
Define the  
function.  This function extracts the second member
       of an ordered pair.  (Contributed by SF, 5-Jan-2015.)
 | 
             
         
         | 
|   | 
| Theorem | xpeq1 4799 | 
Equality theorem for cross product.  (Contributed by NM, 4-Jul-1994.)
 | 
                    
          | 
|   | 
| Theorem | xpeq2 4800 | 
Equality theorem for cross product.  (Contributed by NM, 5-Jul-1994.)
 | 
                    
          |