Theorem nd5 1832

Description: A lemma for proving conditionless ZFC axioms. (Contributed by NM, 8-Jan-2002.)

Assertion

Ref	Expression
nd5	|- ( -. A. y y = x -> ( z = y -> A. x z = y ) )

Distinct variable group:   x, z

Proof of Theorem nd5

Step	Hyp	Ref	Expression
1		dveeq2 1829	. 2 |- ( -. A. x x = y -> ( z = y -> A. x z = y ) )
2	1	nalequcoms 1531	1 |- ( -. A. y y = x -> ( z = y -> A. x z = y ) )

Syntax hints:   -. wn 3   -> wi 4   A.wal 1362   = wceq 1364

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-in1 615  ax-in2 616  ax-io 710  ax-5 1461  ax-7 1462  ax-gen 1463  ax-ie1 1507  ax-ie2 1508  ax-8 1518  ax-10 1519  ax-11 1520  ax-i12 1521  ax-4 1524  ax-17 1540  ax-i9 1544  ax-ial 1548

This theorem depends on definitions:  df-bi 117  df-nf 1475  df-sb 1777

This theorem is referenced by: (None)