Theorem ax12 1526

Description: Rederive the original version of the axiom from ax-i12 1521. (Contributed by Mario Carneiro, 3-Feb-2015.)

Assertion

Ref	Expression
ax12	|- ( -. A. z z = x -> ( -. A. z z = y -> ( x = y -> A. z x = y ) ) )

Proof of Theorem ax12

Step	Hyp	Ref	Expression
1		ax12or 1522	. . . 4 |- ( A. z z = x \/ ( A. z z = y \/ A. z ( x = y -> A. z x = y ) ) )
2	1	ori 724	. . 3 |- ( -. A. z z = x -> ( A. z z = y \/ A. z ( x = y -> A. z x = y ) ) )
3	2	ord 725	. 2 |- ( -. A. z z = x -> ( -. A. z z = y -> A. z ( x = y -> A. z x = y ) ) )
4		ax-4 1524	. 2 |- ( A. z ( x = y -> A. z x = y ) -> ( x = y -> A. z x = y ) )
5	3, 4	syl6 33	1 |- ( -. A. z z = x -> ( -. A. z z = y -> ( x = y -> A. z x = y ) ) )

Syntax hints:   -. wn 3   -> wi 4   \/ wo 709   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-in2 616  ax-io 710  ax-i12 1521  ax-4 1524

This theorem depends on definitions:  df-bi 117

This theorem is referenced by: (None)