Theorem eubidh 1954

Description: Formula-building rule for unique existential quantifier (deduction form). (Contributed by NM, 9-Jul-1994.)

Hypotheses

Ref	Expression
eubidh.1	|- ( ph -> A. x ph )
eubidh.2	|- ( ph -> ( ps <-> ch ) )

Assertion

Ref	Expression
eubidh	|- ( ph -> ( E! x ps <-> E! x ch ) )

Proof of Theorem eubidh

Dummy variable y is distinct from all other variables.

Step	Hyp	Ref	Expression
1		eubidh.1	. . . 4 |- ( ph -> A. x ph )
2		eubidh.2	. . . . 5 |- ( ph -> ( ps <-> ch ) )
3	2	bibi1d 231	. . . 4 |- ( ph -> ( ( ps <-> x = y ) <-> ( ch <-> x = y ) ) )
4	1, 3	albidh 1414	. . 3 |- ( ph -> ( A. x ( ps <-> x = y ) <-> A. x ( ch <-> x = y ) ) )
5	4	exbidv 1753	. 2 |- ( ph -> ( E. y A. x ( ps <-> x = y ) <-> E. y A. x ( ch <-> x = y ) ) )
6		df-eu 1951	. 2 |- ( E! x ps <-> E. y A. x ( ps <-> x = y ) )
7		df-eu 1951	. 2 |- ( E! x ch <-> E. y A. x ( ch <-> x = y ) )
8	5, 6, 7	3bitr4g 221	1 |- ( ph -> ( E! x ps <-> E! x ch ) )

Syntax hints:   -> wi 4   <-> wb 103   A.wal 1287   E.wex 1426   E!weu 1948

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-5 1381  ax-gen 1383  ax-ie1 1427  ax-ie2 1428  ax-4 1445  ax-17 1464  ax-ial 1472

This theorem depends on definitions:  df-bi 115  df-eu 1951

This theorem is referenced by:  euor  1974  mobidh  1982  euan  2004  euor2  2006  eupickbi  2030