Theorem bdreu 13890

Description: Boundedness of existential uniqueness.

Remark regarding restricted quantifiers: the formula A. x e. A ph need not be bounded even if A and ph are. Indeed, _V is bounded by bdcvv 13892, and |- ( A. x e. _V ph <-> A. x ph ) (in minimal propositional calculus), so by bd0 13859, if A. x e. _V ph were bounded when ph is bounded, then A. x ph would be bounded as well when ph is bounded, which is not the case. The same remark holds with E. , E! , E*. (Contributed by BJ, 16-Oct-2019.)

Hypothesis

Ref	Expression
bdreu.1	|- BOUNDED ph

Assertion

Ref	Expression
bdreu	|- BOUNDED E! x e. y ph

Distinct variable group:   x, y

Allowed substitution hints:   ph( x, y)

Proof of Theorem bdreu

Dummy variable z is distinct from all other variables.

Step	Hyp	Ref	Expression
1		bdreu.1	. . . 4 |- BOUNDED ph
2	1	ax-bdex 13854	. . 3 |- BOUNDED E. x e. y ph
3		ax-bdeq 13855	. . . . . 6 |- BOUNDED x = z
4	1, 3	ax-bdim 13849	. . . . 5 |- BOUNDED ( ph -> x = z )
5	4	ax-bdal 13853	. . . 4 |- BOUNDED A. x e. y ( ph -> x = z )
6	5	ax-bdex 13854	. . 3 |- BOUNDED E. z e. y A. x e. y ( ph -> x = z )
7	2, 6	ax-bdan 13850	. 2 |- BOUNDED ( E. x e. y ph /\ E. z e. y A. x e. y ( ph -> x = z ) )
8		reu3 2920	. 2 |- ( E! x e. y ph <-> ( E. x e. y ph /\ E. z e. y A. x e. y ( ph -> x = z ) ) )
9	7, 8	bd0r 13860	1 |- BOUNDED E! x e. y ph

Syntax hints:   -> wi 4   /\ wa 103   A.wral 2448   E.wrex 2449   E!wreu 2450  BOUNDED wbd 13847

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-io 704  ax-5 1440  ax-7 1441  ax-gen 1442  ax-ie1 1486  ax-ie2 1487  ax-8 1497  ax-10 1498  ax-11 1499  ax-i12 1500  ax-bndl 1502  ax-4 1503  ax-17 1519  ax-i9 1523  ax-ial 1527  ax-i5r 1528  ax-ext 2152  ax-bd0 13848  ax-bdim 13849  ax-bdan 13850  ax-bdal 13853  ax-bdex 13854  ax-bdeq 13855

This theorem depends on definitions:  df-bi 116  df-nf 1454  df-sb 1756  df-eu 2022  df-mo 2023  df-cleq 2163  df-clel 2166  df-ral 2453  df-rex 2454  df-reu 2455  df-rmo 2456

This theorem is referenced by:  bdrmo  13891