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Theorem con4i 122

Description: Inference rule derived from axiom ax-3 7. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Wolf Lammen, 21-Jun-2013.)

Hypothesis

Ref	Expression
con4i.1

Assertion

Ref	Expression
con4i

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Proof of Theorem con4i

Step	Hyp	Ref	Expression
1		notnot1 114	. 2
2		con4i.1	. 2
3	1, 2	nsyl2 119	1

Colors of variables: wff setvar class

Syntax hints:   wn 3   wi 4

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

This theorem is referenced by:  pm2.21i  123  mt4  129  modal-b  1752  ax10lem2  1937  ax9from9o  2148  ax67to7  2168  ax467to7  2172  necon2ai  2561  ndmfvrcl  5350  oprssdm  5612  ndmovrcl  5616

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