Theorem excom 1710

Description: Theorem 19.11 of [Margaris] p. 89. (Contributed by NM, 5-Aug-1993.)

Assertion

Ref	Expression
excom	|- ( E. x E. y ph <-> E. y E. x ph )

Proof of Theorem excom

Step	Hyp	Ref	Expression
1		excomim 1709	. 2 |- ( E. x E. y ph -> E. y E. x ph )
2		excomim 1709	. 2 |- ( E. y E. x ph -> E. x E. y ph )
3	1, 2	impbii 126	1 |- ( E. x E. y ph <-> E. y E. x ph )

Syntax hints:   <-> wb 105   E.wex 1538

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-5 1493  ax-7 1494  ax-gen 1495  ax-ie1 1539  ax-ie2 1540  ax-4 1556  ax-ial 1580

This theorem depends on definitions:  df-bi 117

This theorem is referenced by:  excom13  1735  exrot3  1736  ee4anv  1985  sbexyz  2054  2exsb  2060  2euex  2165  2exeu  2170  2eu4  2171  rexcomf  2693  gencbvex  2847  euxfr2dc  2988  euind  2990  sbccomlem  3103  opelopabsbALT  4347  uniuni  4542  elvvv  4782  elco  4888  dmuni  4933  dm0rn0  4940  dmmrnm  4943  dmcosseq  4996  elres  5041  rnco  5235  coass  5247  oprabid  6033  dfoprab2  6051  opabex3d  6266  opabex3  6267  cnvoprab  6380  domen  6900  xpassen  6989  prarloc  7690  fisumcom2  11949  fprodcom2fi  12137