Theorem necon3adOLD 2668

Description: Obsolete proof of necon3ad 2667 as of 23-Nov-2019. (Contributed by NM, 2-Apr-2007.) (Proof shortened by Andrew Salmon, 25-May-2011.) (Proof modification is discouraged.) (New usage is discouraged.)

Hypothesis

Ref	Expression
necon3ad.1

Assertion

Ref	Expression
necon3adOLD

Proof of Theorem necon3adOLD

Step	Hyp	Ref	Expression
1		necon3ad.1	. . 3
2		nne 2658	. . 3
3	1, 2	syl6ibr 227	. 2
4	3	con2d 115	1

Syntax hints:  -.wn 3  ->wi 4  =wceq 1395  =/=wne 2652

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem depends on definitions:  df-bi 185  df-ne 2654