Theorem dveeq1 1940

Description: Quantifier introduction when one pair of variables is distinct. (Contributed by NM, 2-Jan-2002.) (Proof rewritten by Jim Kingdon, 19-Feb-2018.)

Assertion

Ref	Expression
dveeq1	|- ( -. A. x x = y -> ( y = z -> A. x y = z ) )

Distinct variable group:   x, z

Proof of Theorem dveeq1

Step	Hyp	Ref	Expression
1		dveeq2 1740	. 2 |- ( -. A. x x = y -> ( z = y -> A. x z = y ) )
2		equcom 1637	. 2 |- ( z = y <-> y = z )
3	2	albii 1402	. 2 |- ( A. x z = y <-> A. x y = z )
4	1, 2, 3	3imtr3g 202	1 |- ( -. A. x x = y -> ( y = z -> A. x y = z ) )

Syntax hints:   -. wn 3   -> wi 4   A.wal 1285

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-in2 578  ax-io 663  ax-5 1379  ax-7 1380  ax-gen 1381  ax-ie1 1425  ax-ie2 1426  ax-8 1438  ax-10 1439  ax-11 1440  ax-i12 1441  ax-4 1443  ax-17 1462  ax-i9 1466  ax-ial 1470

This theorem depends on definitions:  df-bi 115  df-nf 1393  df-sb 1690

This theorem is referenced by:  sbal2  1943