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Theorem mt3 171
Description: A rule similar to modus tollens. (Contributed by NM, 18-May-1994.) (Proof shortened by Wolf Lammen, 11-Sep-2013.)
Hypotheses
Ref Expression
mt3.1
mt3.2
Assertion
Ref Expression
mt3

Proof of Theorem mt3
StepHypRef Expression
1 mt3.1 . . 3
2 mt3.2 . . 3
31, 2mto 167 . 2
43notnotri 106 1
Colors of variables: wff setvar class
Syntax hints:   wn 3   wi 4
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem is referenced by:  equidOLD  1677  spOLD  1748  spimehOLD  1821  cbv3hvOLD  1851  ax9  1949  equidq  2175
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