Theorem dfss2f 2056

Description: Equivalence for subclass relation, using bound-variable hypotheses instead of distinct variable conditions.

Hypotheses

Ref	Expression
dfss2f.1	|- (y e. A -> A.x y e. A)
dfss2f.2	|- (y e. B -> A.x y e. B)

Assertion

Ref	Expression
dfss2f	|- (A (_ B <-> A.x(x e. A -> x e. B))

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

Proof of Theorem dfss2f

Step	Hyp	Ref	Expression
1		dfss2 2054	. 2 |- (A (_ B <-> A.y(y e. A -> y e. B))
2		ax-17 969	. . 3 |- ((x e. A -> x e. B) -> A.y(x e. A -> x e. B))
3		dfss2f.1	. . . 4 |- (y e. A -> A.x y e. A)
4		dfss2f.2	. . . 4 |- (y e. B -> A.x y e. B)
5	3, 4	hbim 1005	. . 3 |- ((y e. A -> y e. B) -> A.x(y e. A -> y e. B))
6		eleq1 1531	. . . 4 |- (x = y -> (x e. A <-> y e. A))
7		eleq1 1531	. . . 4 |- (x = y -> (x e. B <-> y e. B))
8	6, 7	imbi12d 625	. . 3 |- (x = y -> ((x e. A -> x e. B) <-> (y e. A -> y e. B)))
9	2, 5, 8	cbval 1163	. 2 |- (A.x(x e. A -> x e. B) <-> A.y(y e. A -> y e. B))
10	1, 9	bitr4 176	1 |- (A (_ B <-> A.x(x e. A -> x e. B))

Syntax hints:   -> wi 3   <-> wb 146  A.wal 952   = wceq 954   e. wcel 956   (_ wss 2043

This theorem is referenced by:  dfss3f 2057  hbss 2058  ss2ab 2112  fopab2 3814  iunon 3900  iinon 3901  rankval4 4682  scott0 4697

This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7  ax-7 960  ax-gen 961  ax-8 962  ax-10 964  ax-12 966  ax-17 969  ax-4 971  ax-5o 973  ax-6o 976  ax-9o 1121  ax-10o 1138  ax-16 1208  ax-11o 1216  ax-ext 1457

This theorem depends on definitions:  df-bi 147  df-an 225  df-ex 979  df-sb 1170  df-clab 1462  df-cleq 1467  df-clel 1470  df-in 2047  df-ss 2049

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