Theorem rabsnel 29341

Description: Truth implied by equality of a restricted class abstraction and a singleton. (Contributed by Thierry Arnoux, 15-Sep-2018.)

Hypothesis

Ref	Expression
rabsnel.1	|- B e. _V

Assertion

Ref	Expression
rabsnel	|- ( { x e. A | ph } = { B } -> B e. A )

Distinct variable groups:   x, A   x, B

Allowed substitution hint:   ph( x)

Proof of Theorem rabsnel

Step	Hyp	Ref	Expression
1		rabsnel.1	. . . 4 |- B e. _V
2	1	snid 4208	. . 3 |- B e. { B }
3		eleq2 2690	. . 3 |- ( { x e. A | ph } = { B } -> ( B e. { x e. A | ph } <-> B e. { B } ) )
4	2, 3	mpbiri 248	. 2 |- ( { x e. A | ph } = { B } -> B e. { x e. A | ph } )
5		elrabi 3359	. 2 |- ( B e. { x e. A | ph } -> B e. A )
6	4, 5	syl 17	1 |- ( { x e. A | ph } = { B } -> B e. A )

Syntax hints:   -> wi 4   = wceq 1483   e. wcel 1990   {crab 2916   _Vcvv 3200   {csn 4177

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737  ax-5 1839  ax-6 1888  ax-7 1935  ax-9 1999  ax-10 2019  ax-11 2034  ax-12 2047  ax-13 2246  ax-ext 2602

This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-tru 1486  df-ex 1705  df-nf 1710  df-sb 1881  df-clab 2609  df-cleq 2615  df-clel 2618  df-nfc 2753  df-rab 2921  df-v 3202  df-sn 4178

This theorem is referenced by:  ddemeas  30299