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Theorem mo3 2187
Description: Alternate definition of "at most one." Definition of [BellMachover] p. 460, except that definition has the side condition that  y not occur in  ph in place of our hypothesis. (Contributed by NM, 8-Mar-1995.)
Hypothesis
Ref Expression
mo3.1  |-  F/ y
ph
Assertion
Ref Expression
mo3  |-  ( E* x ph  <->  A. x A. y ( ( ph  /\ 
[ y  /  x ] ph )  ->  x  =  y ) )
Distinct variable group:    x, y
Allowed substitution hints:    ph( x, y)

Proof of Theorem mo3
StepHypRef Expression
1 mo3.1 . . 3  |-  F/ y
ph
21mo2 2185 . 2  |-  ( E* x ph  <->  E. y A. x ( ph  ->  x  =  y ) )
31mo 2178 . 2  |-  ( E. y A. x (
ph  ->  x  =  y )  <->  A. x A. y
( ( ph  /\  [ y  /  x ] ph )  ->  x  =  y ) )
42, 3bitri 240 1  |-  ( E* x ph  <->  A. x A. y ( ( ph  /\ 
[ y  /  x ] ph )  ->  x  =  y ) )
Colors of variables: wff set class
Syntax hints:    -> wi 4    <-> wb 176    /\ wa 358   A.wal 1530   E.wex 1531   F/wnf 1534   [wsb 1638   E*wmo 2157
This theorem is referenced by:  mo4f  2188  mopick  2218  rmo3  3091  isarep2  5348  mo5f  23159  rmo3f  23194  rmo4fOLD  23195  isconcl5a  26204  isconcl5ab  26205  pm14.12  27724  bnj580  29261
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1536  ax-5 1547  ax-17 1606  ax-9 1644  ax-8 1661  ax-6 1715  ax-7 1720  ax-11 1727  ax-12 1878
This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-tru 1310  df-ex 1532  df-nf 1535  df-sb 1639  df-eu 2160  df-mo 2161
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