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Theorem equs5e 1916
Description: A property related to substitution that unlike equs5 2049 doesn't require a distinctor antecedent. (Contributed by NM, 2-Feb-2007.) (Proof shortened by Wolf Lammen, 15-Jan-2018.)
Assertion
Ref Expression
equs5e  |-  ( E. x ( x  =  y  /\  ph )  ->  A. x ( x  =  y  ->  E. y ph ) )

Proof of Theorem equs5e
StepHypRef Expression
1 nfa1 1833 . 2  |-  F/ x A. x ( x  =  y  ->  E. y ph )
2 hbe1 1779 . . . . 5  |-  ( E. y ph  ->  A. y E. y ph )
3219.23bi 1807 . . . 4  |-  ( ph  ->  A. y E. y ph )
4 ax-12 1794 . . . 4  |-  ( x  =  y  ->  ( A. y E. y ph  ->  A. x ( x  =  y  ->  E. y ph ) ) )
53, 4syl5 32 . . 3  |-  ( x  =  y  ->  ( ph  ->  A. x ( x  =  y  ->  E. y ph ) ) )
65imp 429 . 2  |-  ( ( x  =  y  /\  ph )  ->  A. x
( x  =  y  ->  E. y ph )
)
71, 6exlimi 1847 1  |-  ( E. x ( x  =  y  /\  ph )  ->  A. x ( x  =  y  ->  E. y ph ) )
Colors of variables: wff setvar class
Syntax hints:    -> wi 4    /\ wa 369   A.wal 1368   E.wex 1587
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1592  ax-4 1603  ax-5 1671  ax-6 1710  ax-7 1730  ax-10 1777  ax-12 1794
This theorem depends on definitions:  df-bi 185  df-an 371  df-ex 1588  df-nf 1591
This theorem is referenced by:  sb4e  1951
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