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Theorem 3exdistr 1851
Description: Distribution of existential quantifiers. (Contributed by NM, 9-Mar-1995.) (Proof shortened by Andrew Salmon, 25-May-2011.)
Assertion
Ref Expression
3exdistr  |-  ( E. x E. y E. z ( ph  /\  ps  /\  ch )  <->  E. x
( ph  /\  E. y
( ps  /\  E. z ch ) ) )
Distinct variable groups:    ph, y    ph, z    ps, z
Allowed substitution hints:    ph( x)    ps( x, y)    ch( x, y, z)

Proof of Theorem 3exdistr
StepHypRef Expression
1 3anass 938 . . . 4  |-  ( (
ph  /\  ps  /\  ch ) 
<->  ( ph  /\  ( ps  /\  ch ) ) )
212exbii 1570 . . 3  |-  ( E. y E. z (
ph  /\  ps  /\  ch ) 
<->  E. y E. z
( ph  /\  ( ps  /\  ch ) ) )
3 19.42vv 1848 . . 3  |-  ( E. y E. z (
ph  /\  ( ps  /\ 
ch ) )  <->  ( ph  /\ 
E. y E. z
( ps  /\  ch ) ) )
4 exdistr 1847 . . . 4  |-  ( E. y E. z ( ps  /\  ch )  <->  E. y ( ps  /\  E. z ch ) )
54anbi2i 675 . . 3  |-  ( (
ph  /\  E. y E. z ( ps  /\  ch ) )  <->  ( ph  /\ 
E. y ( ps 
/\  E. z ch )
) )
62, 3, 53bitri 262 . 2  |-  ( E. y E. z (
ph  /\  ps  /\  ch ) 
<->  ( ph  /\  E. y ( ps  /\  E. z ch ) ) )
76exbii 1569 1  |-  ( E. x E. y E. z ( ph  /\  ps  /\  ch )  <->  E. x
( ph  /\  E. y
( ps  /\  E. z ch ) ) )
Colors of variables: wff set class
Syntax hints:    <-> wb 176    /\ wa 358    /\ w3a 934   E.wex 1528
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1533  ax-5 1544  ax-17 1603  ax-9 1635  ax-8 1643  ax-6 1703  ax-11 1715
This theorem depends on definitions:  df-bi 177  df-an 360  df-3an 936  df-ex 1529  df-nf 1532
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