Theorem reuhypd 4456

Description: A theorem useful for eliminating restricted existential uniqueness hypotheses. (Contributed by NM, 16-Jan-2012.)

Hypotheses

Ref	Expression
reuhypd.1	|- ( ( ph /\ x e. C ) -> B e. C )
reuhypd.2	|- ( ( ph /\ x e. C /\ y e. C ) -> ( x = A <-> y = B ) )

Assertion

Ref	Expression
reuhypd	|- ( ( ph /\ x e. C ) -> E! y e. C x = A )

Distinct variable groups:   ph, y   y, B   y, C   x, y

Allowed substitution hints:   ph( x)   A( x, y)   B( x)   C( x)

Proof of Theorem reuhypd

Step	Hyp	Ref	Expression
1		reuhypd.1	. . . . 5 |- ( ( ph /\ x e. C ) -> B e. C )
2		elex 2741	. . . . 5 |- ( B e. C -> B e. _V )
3	1, 2	syl 14	. . . 4 |- ( ( ph /\ x e. C ) -> B e. _V )
4		eueq 2901	. . . 4 |- ( B e. _V <-> E! y y = B )
5	3, 4	sylib 121	. . 3 |- ( ( ph /\ x e. C ) -> E! y y = B )
6		eleq1 2233	. . . . . . 7 |- ( y = B -> ( y e. C <-> B e. C ) )
7	1, 6	syl5ibrcom 156	. . . . . 6 |- ( ( ph /\ x e. C ) -> ( y = B -> y e. C ) )
8	7	pm4.71rd 392	. . . . 5 |- ( ( ph /\ x e. C ) -> ( y = B <-> ( y e. C /\ y = B ) ) )
9		reuhypd.2	. . . . . . 7 |- ( ( ph /\ x e. C /\ y e. C ) -> ( x = A <-> y = B ) )
10	9	3expa 1198	. . . . . 6 |- ( ( ( ph /\ x e. C ) /\ y e. C ) -> ( x = A <-> y = B ) )
11	10	pm5.32da 449	. . . . 5 |- ( ( ph /\ x e. C ) -> ( ( y e. C /\ x = A ) <-> ( y e. C /\ y = B ) ) )
12	8, 11	bitr4d 190	. . . 4 |- ( ( ph /\ x e. C ) -> ( y = B <-> ( y e. C /\ x = A ) ) )
13	12	eubidv 2027	. . 3 |- ( ( ph /\ x e. C ) -> ( E! y y = B <-> E! y ( y e. C /\ x = A ) ) )
14	5, 13	mpbid 146	. 2 |- ( ( ph /\ x e. C ) -> E! y ( y e. C /\ x = A ) )
15		df-reu 2455	. 2 |- ( E! y e. C x = A <-> E! y ( y e. C /\ x = A ) )
16	14, 15	sylibr 133	1 |- ( ( ph /\ x e. C ) -> E! y e. C x = A )

Syntax hints:   -> wi 4   /\ wa 103   <-> wb 104   /\ w3a 973   = wceq 1348   E!weu 2019   e. wcel 2141   E!wreu 2450   _Vcvv 2730

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-io 704  ax-5 1440  ax-7 1441  ax-gen 1442  ax-ie1 1486  ax-ie2 1487  ax-8 1497  ax-10 1498  ax-11 1499  ax-i12 1500  ax-bndl 1502  ax-4 1503  ax-17 1519  ax-i9 1523  ax-ial 1527  ax-i5r 1528  ax-ext 2152

This theorem depends on definitions:  df-bi 116  df-3an 975  df-nf 1454  df-sb 1756  df-eu 2022  df-mo 2023  df-clab 2157  df-cleq 2163  df-clel 2166  df-reu 2455  df-v 2732

This theorem is referenced by:  reuhyp  4457