Theorem mt3 112

Description: A rule similar to modus tollens.

Hypotheses

Ref	Expression
mt3.1	|- -. ps
mt3.2	|- (-. ph -> ps)

Assertion

Ref	Expression
mt3	|- ph

Proof of Theorem mt3

Step	Hyp	Ref	Expression
1		mt3.1	. 2 |- -. ps
2		mt3.2	. . 3 |- (-. ph -> ps)
3	2	con1i 96	. 2 |- (-. ps -> ph)
4	1, 3	ax-mp 7	1 |- ph

Syntax hints:  -. wn 2   -> wi 3

This theorem is referenced by:  ax4 974  omelon 4638  sinhalfpilem 8674

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

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