Theorem nd5 1790

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 1787	. 2 |- ( -. A. x x = y -> ( z = y -> A. x z = y ) )
2	1	nalequcoms 1497	1 |- ( -. A. y y = x -> ( z = y -> A. x z = y ) )

Syntax hints:   -. wn 3   -> wi 4   A.wal 1329   = wceq 1331

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-in1 603  ax-in2 604  ax-io 698  ax-5 1423  ax-7 1424  ax-gen 1425  ax-ie1 1469  ax-ie2 1470  ax-8 1482  ax-10 1483  ax-11 1484  ax-i12 1485  ax-4 1487  ax-17 1506  ax-i9 1510  ax-ial 1514

This theorem depends on definitions:  df-bi 116  df-nf 1437  df-sb 1736

This theorem is referenced by: (None)