Theorem bijust 230

Description: Theorem used to justify definition of biconditional df-bi 232. (The proof was shortened by Josh Purinton, 29-Dec-2000.)

Assertion

Ref	Expression
bijust	|- -. ((ph -> ph) -> -. (ph -> ph))

Proof of Theorem bijust

Step	Hyp	Ref	Expression
1		id 15	. 2 |- (ph -> ph)
2		pm2.01 215	. 2 |- (((ph -> ph) -> -. (ph -> ph)) -> -. (ph -> ph))
3	1, 2	mt2 144	1 |- -. ((ph -> ph) -> -. (ph -> ph))

Syntax hints:  -. wn 2   -> wi 3

This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7

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