Theorem snexALT 4852

Description: Alternate proof of snex 4908 using Power Set (ax-pow 4843) instead of Pairing (ax-pr 4906). Unlike in the proof of zfpair 4904, Replacement (ax-rep 4771) is not needed. (Contributed by NM, 7-Aug-1994.) (Proof shortened by Andrew Salmon, 25-Jul-2011.) (Proof modification is discouraged.) (New usage is discouraged.)

Assertion

Ref	Expression
snexALT	|- { A } e. _V

Proof of Theorem snexALT

Step	Hyp	Ref	Expression
1		snsspw 4375	. . 3 |- { A } C_ ~P A
2		ssexg 4804	. . 3 |- ( ( { A } C_ ~P A /\ ~P A e. _V ) -> { A } e. _V )
3	1, 2	mpan 706	. 2 |- ( ~P A e. _V -> { A } e. _V )
4		pwexg 4850	. . . 4 |- ( A e. _V -> ~P A e. _V )
5	4	con3i 150	. . 3 |- ( -. ~P A e. _V -> -. A e. _V )
6		snprc 4253	. . . . 5 |- ( -. A e. _V <-> { A } = (/) )
7	6	biimpi 206	. . . 4 |- ( -. A e. _V -> { A } = (/) )
8		0ex 4790	. . . 4 |- (/) e. _V
9	7, 8	syl6eqel 2709	. . 3 |- ( -. A e. _V -> { A } e. _V )
10	5, 9	syl 17	. 2 |- ( -. ~P A e. _V -> { A } e. _V )
11	3, 10	pm2.61i 176	1 |- { A } e. _V

Syntax hints:   -. wn 3   = wceq 1483   e. wcel 1990   _Vcvv 3200   C_ wss 3574   (/)c0 3915   ~Pcpw 4158   {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  ax-sep 4781  ax-nul 4789  ax-pow 4843

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-v 3202  df-dif 3577  df-in 3581  df-ss 3588  df-nul 3916  df-pw 4160  df-sn 4178

This theorem is referenced by:  p0exALT  4854