Theorem exrot4 1714

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 1712	. . 3 |- ( E. y E. z E. w ph <-> E. w E. z E. y ph )
2	1	exbii 1628	. 2 |- ( E. x E. y E. z E. w ph <-> E. x E. w E. z E. y ph )
3		excom13 1712	. 2 |- ( E. x E. w E. z E. y ph <-> E. z E. w E. x E. y ph )
4	2, 3	bitri 184	1 |- ( E. x E. y E. z E. w ph <-> E. z E. w E. x E. y ph )

Syntax hints:   <-> wb 105   E.wex 1515

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 1470  ax-7 1471  ax-gen 1472  ax-ie1 1516  ax-ie2 1517  ax-4 1533  ax-ial 1557

This theorem depends on definitions:  df-bi 117

This theorem is referenced by:  ee8anv  1963  elvvv  4738  dfoprab2  5992  xpassen  6925  enq0sym  7545