Theorem ax67 1018

Description: Proof of a single axiom that can replace both ax-6o 976 and ax-7 960. See ax67to6 1019 and ax67to7 1020 for the re-derivation of those axioms.

Assertion

Ref	Expression
ax67	|- (-. A.x -. A.yA.xph -> A.yph)

Proof of Theorem ax67

Step	Hyp	Ref	Expression
1		ax-7 960	. . . . 5 |- (A.yA.xph -> A.xA.yph)
2	1	con3i 98	. . . 4 |- (-. A.xA.yph -> -. A.yA.xph)
3	2	19.20i 990	. . 3 |- (A.x -. A.xA.yph -> A.x -. A.yA.xph)
4	3	con3i 98	. 2 |- (-. A.x -. A.yA.xph -> -. A.x -. A.xA.yph)
5		ax-6o 976	. 2 |- (-. A.x -. A.xA.yph -> A.yph)
6	4, 5	syl 10	1 |- (-. A.x -. A.yA.xph -> A.yph)

Syntax hints:  -. wn 2   -> wi 3  A.wal 952

This theorem is referenced by:  ax67to6 1019  ax67to7 1020

This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7  ax-7 960  ax-gen 961  ax-4 971  ax-5o 973  ax-6o 976

Copyright terms: Public domain