Theorem dveel2 2151

Description: Quantifier introduction when one pair of variables is disjoint. (Contributed by NM, 2-Jan-2002.)

Assertion

Ref	Expression
dveel2	|- ( -. A. x x = y -> ( z e. y -> A. x z e. y ) )

Distinct variable group:   x, z

Proof of Theorem dveel2

Dummy variable w is distinct from all other variables.

Step	Hyp	Ref	Expression
1		ax-17 1519	. 2 |- ( z e. w -> A. x z e. w )
2		ax-17 1519	. 2 |- ( z e. y -> A. w z e. y )
3		elequ2 2146	. 2 |- ( w = y -> ( z e. w <-> z e. y ) )
4	1, 2, 3	dvelimf 2008	1 |- ( -. A. x x = y -> ( z e. y -> A. x z e. y ) )

Syntax hints:   -. wn 3   -> wi 4   A.wal 1346

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-in2 610  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-14 2144

This theorem depends on definitions:  df-bi 116  df-nf 1454  df-sb 1756

This theorem is referenced by: (None)