Theorem exrot4 1679

Description: Rotate existential quantifiers twice. (Contributed by NM, 9-Mar-1995.)

Assertion

Ref	Expression
exrot4	|- ( E. x E. y E. z E. w ph <-> E. z E. w E. x E. y ph )

Proof of Theorem exrot4

Step	Hyp	Ref	Expression
1		excom13 1677	. . 3 |- ( E. y E. z E. w ph <-> E. w E. z E. y ph )
2	1	exbii 1593	. 2 |- ( E. x E. y E. z E. w ph <-> E. x E. w E. z E. y ph )
3		excom13 1677	. 2 |- ( E. x E. w E. z E. y ph <-> E. z E. w E. x E. y ph )
4	2, 3	bitri 183	1 |- ( E. x E. y E. z E. w ph <-> E. z E. w E. x E. y ph )

Syntax hints:   <-> wb 104   E.wex 1480

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-5 1435  ax-7 1436  ax-gen 1437  ax-ie1 1481  ax-ie2 1482  ax-4 1498  ax-ial 1522

This theorem depends on definitions:  df-bi 116

This theorem is referenced by:  ee8anv  1923  elvvv  4667  dfoprab2  5889  xpassen  6796  enq0sym  7373