Theorem dfnotOLD 1415

Description: Obsolete proof of dfnot 1414 as of 21-Jul-2019. (Contributed by Mario Carneiro, 9-Feb-2017.) (New usage is discouraged.) (Proof modification is discouraged.)

Assertion

Ref	Expression
dfnotOLD

Proof of Theorem dfnotOLD

Step	Hyp	Ref	Expression
1		pm2.21 108	. 2
2		id 22	. . 3
3		falim 1409	. . 3
4	2, 3	ja 161	. 2
5	1, 4	impbii 188	1

Syntax hints:  -.wn 3  ->wi 4  <->wb 184  wfal 1400

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-tru 1398  df-fal 1401