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Theorem mt4 129

Description: The rule of modus tollens. (Contributed by Wolf Lammen, 12-May-2013.)

**Hypotheses**
Ref	Expression
mt4.1
mt4.2

**Assertion**
Ref	Expression
mt4

**Proof of Theorem mt4**
Step	Hyp	Ref	Expression
1		mt4.1	. 2
2		mt4.2	. . 3
3	2	con4i 122	. 2
4	1, 3	ax-mp 5	1

Colors of variables: wff setvar class

This proof depends on syntax axioms:

wn 3

wi 4

This proof depends on axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8

This theorem is used by: (None)