Theorem alex 1075

Description: Theorem 19.6 of [Margaris] p. 89.

Assertion

Ref	Expression
alex	|- (A.xph <-> -. E.x -. ph)

Proof of Theorem alex

Step	Hyp	Ref	Expression
1		notnot 168	. . 3 |- (ph <-> -. -. ph)
2	1	albii 1040	. 2 |- (A.xph <-> A.x -. -. ph)
3		alnex 1074	. 2 |- (A.x -. -. ph <-> -. E.x -. ph)
4	2, 3	bitri 180	1 |- (A.xph <-> -. E.x -. ph)

Syntax hints:  -. wn 2   <-> wb 153  A.wal 995  E.wex 1021

This theorem is referenced by:  exnal 1079

This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7  ax-gen 1004  ax-4 1014  ax-5o 1016

This theorem depends on definitions:  df-bi 154  df-an 232  df-ex 1022

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