Theorem rexab2 2939

Description: Existential quantification over a class abstraction. (Contributed by Mario Carneiro, 3-Sep-2015.)

Hypothesis

Ref	Expression
ralab2.1	|- ( x = y -> ( ps <-> ch ) )

Assertion

Ref	Expression
rexab2	|- ( E. x e. { y | ph } ps <-> E. y ( ph /\ ch ) )

Distinct variable groups:   x, y   ch, x   ph, x   ps, y

Allowed substitution hints:   ph( y)   ps( x)   ch( y)

Proof of Theorem rexab2

Step	Hyp	Ref	Expression
1		df-rex 2490	. 2 |- ( E. x e. { y | ph } ps <-> E. x ( x e. { y | ph } /\ ps ) )
2		nfsab1 2195	. . . 4 |- F/ y x e. { y | ph }
3		nfv 1551	. . . 4 |- F/ y ps
4	2, 3	nfan 1588	. . 3 |- F/ y ( x e. { y | ph } /\ ps )
5		nfv 1551	. . 3 |- F/ x ( ph /\ ch )
6		eleq1 2268	. . . . 5 |- ( x = y -> ( x e. { y | ph } <-> y e. { y | ph } ) )
7		abid 2193	. . . . 5 |- ( y e. { y | ph } <-> ph )
8	6, 7	bitrdi 196	. . . 4 |- ( x = y -> ( x e. { y | ph } <-> ph ) )
9		ralab2.1	. . . 4 |- ( x = y -> ( ps <-> ch ) )
10	8, 9	anbi12d 473	. . 3 |- ( x = y -> ( ( x e. { y | ph } /\ ps ) <-> ( ph /\ ch ) ) )
11	4, 5, 10	cbvex 1779	. 2 |- ( E. x ( x e. { y | ph } /\ ps ) <-> E. y ( ph /\ ch ) )
12	1, 11	bitri 184	1 |- ( E. x e. { y | ph } ps <-> E. y ( ph /\ ch ) )

Syntax hints:   -> wi 4   /\ wa 104   <-> wb 105   E.wex 1515   e. wcel 2176   {cab 2191   E.wrex 2485

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-5 1470  ax-7 1471  ax-gen 1472  ax-ie1 1516  ax-ie2 1517  ax-8 1527  ax-11 1529  ax-4 1533  ax-17 1549  ax-i9 1553  ax-ial 1557  ax-ext 2187

This theorem depends on definitions:  df-bi 117  df-nf 1484  df-sb 1786  df-clab 2192  df-cleq 2198  df-clel 2201  df-rex 2490

This theorem is referenced by:  rexrab2  2940