Theorem mtbii 685

Description: An inference from a biconditional, similar to modus tollens. (Contributed by NM, 27-Nov-1995.)

Hypotheses

Ref	Expression
mtbii.min	|- -. ps
mtbii.maj	|- ( ph -> ( ps <-> ch ) )

Assertion

Ref	Expression
mtbii	|- ( ph -> -. ch )

Proof of Theorem mtbii

Step	Hyp	Ref	Expression
1		mtbii.min	. 2 |- -. ps
2		mtbii.maj	. . 3 |- ( ph -> ( ps <-> ch ) )
3	2	biimprd 158	. 2 |- ( ph -> ( ch -> ps ) )
4	1, 3	mtoi 674	1 |- ( ph -> -. ch )

This proof depends on syntax axioms:   -. wn 3   -> wi 4   <-> wb 105

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 623  ax-in2 624

This proof depends on definitions:  df-bi 117

This theorem is used by:  onsucelsucexmid  4677  nntri2  6767  nntri3  6770  nndceq  6772  inffiexmid  7213  genpdisj  7891  ltposr  8131  hashennn  11235  fsumsplit  12193  sumsplitdc  12218  fprodm1  12384  m1dvdsndvds  13050  ballotfilemi1  13297  ballotfilemii  13298  chtqub  16257