Theorem zfauscl 2673

Description: Separation Scheme using a class variable. To derive this from ax-sep 2671, we invoke the Axiom of Extensionality (indirectly via vtocl 1817), which is needed for the justification of class variable notation.

If we omit the requirement that y not occur in ph, we can derive a contradiction, as notzfaus 2709 shows.

Hypothesis

Ref	Expression
zfauscl.1	|- A e. V

Assertion

Ref	Expression
zfauscl	|- E.yA.x(x e. y <-> (x e. A /\ ph))

Distinct variable groups:   x,y,A   ph,y

Proof of Theorem zfauscl

Step	Hyp	Ref	Expression
1		zfauscl.1	. 2 |- A e. V
2		eleq2 1511	. . . . . 6 |- (z = A -> (x e. z <-> x e. A))
3	2	anbi1d 615	. . . . 5 |- (z = A -> ((x e. z /\ ph) <-> (x e. A /\ ph)))
4	3	bibi2d 616	. . . 4 |- (z = A -> ((x e. y <-> (x e. z /\ ph)) <-> (x e. y <-> (x e. A /\ ph))))
5	4	albidv 1260	. . 3 |- (z = A -> (A.x(x e. y <-> (x e. z /\ ph)) <-> A.x(x e. y <-> (x e. A /\ ph))))
6	5	exbidv 1261	. 2 |- (z = A -> (E.yA.x(x e. y <-> (x e. z /\ ph)) <-> E.yA.x(x e. y <-> (x e. A /\ ph))))
7		ax-sep 2671	. 2 |- E.yA.x(x e. y <-> (x e. z /\ ph))
8	1, 6, 7	vtocl 1817	1 |- E.yA.x(x e. y <-> (x e. A /\ ph))

Syntax hints:   <-> wb 146   /\ wa 223  A.wal 950  E.wex 956   = wceq 1099   e. wcel 1105  Vcvv 1786

This theorem is referenced by:  nalset 2680  inex1 2684

This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7  ax-4 951  ax-5 952  ax-6 953  ax-gen 955  ax-9 1102  ax-12 1104  ax-17 1190  ax-ext 1436  ax-sep 2671

This theorem depends on definitions:  df-bi 147  df-an 225  df-ex 957  df-sb 1155  df-clab 1441  df-cleq 1446  df-clel 1449  df-v 1787

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