Theorem iss 4988

Description: A subclass of the identity function is the identity function restricted to its domain. (Contributed by NM, 13-Dec-2003.) (Proof shortened by Andrew Salmon, 27-Aug-2011.)

Assertion

Ref	Expression
iss	|- ( A C_ _I <-> A = ( _I |` dom A ) )

Proof of Theorem iss

Dummy variables x y are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		ssel 3173	. . . . . . 7 |- ( A C_ _I -> ( <. x , y >. e. A -> <. x , y >. e. _I ) )
2		vex 2763	. . . . . . . . 9 |- x e. _V
3		vex 2763	. . . . . . . . 9 |- y e. _V
4	2, 3	opeldm 4865	. . . . . . . 8 |- ( <. x , y >. e. A -> x e. dom A )
5	4	a1i 9	. . . . . . 7 |- ( A C_ _I -> ( <. x , y >. e. A -> x e. dom A ) )
6	1, 5	jcad 307	. . . . . 6 |- ( A C_ _I -> ( <. x , y >. e. A -> ( <. x , y >. e. _I /\ x e. dom A ) ) )
7		df-br 4030	. . . . . . . . 9 |- ( x _I y <-> <. x , y >. e. _I )
8	3	ideq 4814	. . . . . . . . 9 |- ( x _I y <-> x = y )
9	7, 8	bitr3i 186	. . . . . . . 8 |- ( <. x , y >. e. _I <-> x = y )
10	2	eldm2 4860	. . . . . . . . . 10 |- ( x e. dom A <-> E. y <. x , y >. e. A )
11		opeq2 3805	. . . . . . . . . . . . . . 15 |- ( x = y -> <. x , x >. = <. x , y >. )
12	11	eleq1d 2262	. . . . . . . . . . . . . 14 |- ( x = y -> ( <. x , x >. e. A <-> <. x , y >. e. A ) )
13	12	biimprcd 160	. . . . . . . . . . . . 13 |- ( <. x , y >. e. A -> ( x = y -> <. x , x >. e. A ) )
14	9, 13	biimtrid 152	. . . . . . . . . . . 12 |- ( <. x , y >. e. A -> ( <. x , y >. e. _I -> <. x , x >. e. A ) )
15	1, 14	sylcom 28	. . . . . . . . . . 11 |- ( A C_ _I -> ( <. x , y >. e. A -> <. x , x >. e. A ) )
16	15	exlimdv 1830	. . . . . . . . . 10 |- ( A C_ _I -> ( E. y <. x , y >. e. A -> <. x , x >. e. A ) )
17	10, 16	biimtrid 152	. . . . . . . . 9 |- ( A C_ _I -> ( x e. dom A -> <. x , x >. e. A ) )
18	12	imbi2d 230	. . . . . . . . 9 |- ( x = y -> ( ( x e. dom A -> <. x , x >. e. A ) <-> ( x e. dom A -> <. x , y >. e. A ) ) )
19	17, 18	syl5ibcom 155	. . . . . . . 8 |- ( A C_ _I -> ( x = y -> ( x e. dom A -> <. x , y >. e. A ) ) )
20	9, 19	biimtrid 152	. . . . . . 7 |- ( A C_ _I -> ( <. x , y >. e. _I -> ( x e. dom A -> <. x , y >. e. A ) ) )
21	20	impd 254	. . . . . 6 |- ( A C_ _I -> ( ( <. x , y >. e. _I /\ x e. dom A ) -> <. x , y >. e. A ) )
22	6, 21	impbid 129	. . . . 5 |- ( A C_ _I -> ( <. x , y >. e. A <-> ( <. x , y >. e. _I /\ x e. dom A ) ) )
23	3	opelres 4947	. . . . 5 |- ( <. x , y >. e. ( _I |` dom A ) <-> ( <. x , y >. e. _I /\ x e. dom A ) )
24	22, 23	bitr4di 198	. . . 4 |- ( A C_ _I -> ( <. x , y >. e. A <-> <. x , y >. e. ( _I |` dom A ) ) )
25	24	alrimivv 1886	. . 3 |- ( A C_ _I -> A. x A. y ( <. x , y >. e. A <-> <. x , y >. e. ( _I |` dom A ) ) )
26		reli 4791	. . . . 5 |- Rel _I
27		relss 4746	. . . . 5 |- ( A C_ _I -> ( Rel _I -> Rel A ) )
28	26, 27	mpi 15	. . . 4 |- ( A C_ _I -> Rel A )
29		relres 4970	. . . 4 |- Rel ( _I |` dom A )
30		eqrel 4748	. . . 4 |- ( ( Rel A /\ Rel ( _I |` dom A ) ) -> ( A = ( _I |` dom A ) <-> A. x A. y ( <. x , y >. e. A <-> <. x , y >. e. ( _I |` dom A ) ) ) )
31	28, 29, 30	sylancl 413	. . 3 |- ( A C_ _I -> ( A = ( _I |` dom A ) <-> A. x A. y ( <. x , y >. e. A <-> <. x , y >. e. ( _I |` dom A ) ) ) )
32	25, 31	mpbird 167	. 2 |- ( A C_ _I -> A = ( _I |` dom A ) )
33		resss 4966	. . 3 |- ( _I |` dom A ) C_ _I
34		sseq1 3202	. . 3 |- ( A = ( _I |` dom A ) -> ( A C_ _I <-> ( _I |` dom A ) C_ _I ) )
35	33, 34	mpbiri 168	. 2 |- ( A = ( _I |` dom A ) -> A C_ _I )
36	32, 35	impbii 126	1 |- ( A C_ _I <-> A = ( _I |` dom A ) )

Syntax hints:   -> wi 4   /\ wa 104   <-> wb 105   A.wal 1362   = wceq 1364   E.wex 1503   e. wcel 2164   C_ wss 3153   <.cop 3621   class class class wbr 4029   _I cid 4319   dom cdm 4659   |` cres 4661   Rel wrel 4664

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-io 710  ax-5 1458  ax-7 1459  ax-gen 1460  ax-ie1 1504  ax-ie2 1505  ax-8 1515  ax-10 1516  ax-11 1517  ax-i12 1518  ax-bndl 1520  ax-4 1521  ax-17 1537  ax-i9 1541  ax-ial 1545  ax-i5r 1546  ax-14 2167  ax-ext 2175  ax-sep 4147  ax-pow 4203  ax-pr 4238

This theorem depends on definitions:  df-bi 117  df-3an 982  df-tru 1367  df-nf 1472  df-sb 1774  df-eu 2045  df-mo 2046  df-clab 2180  df-cleq 2186  df-clel 2189  df-nfc 2325  df-ral 2477  df-rex 2478  df-v 2762  df-un 3157  df-in 3159  df-ss 3166  df-pw 3603  df-sn 3624  df-pr 3625  df-op 3627  df-br 4030  df-opab 4091  df-id 4324  df-xp 4665  df-rel 4666  df-dm 4669  df-res 4671

This theorem is referenced by:  funcocnv2  5525