Theorem sspwb 4176

Description: Classes are subclasses if and only if their power classes are subclasses. Exercise 18 of [TakeutiZaring] p. 18. (Contributed by NM, 13-Oct-1996.)

Assertion

Ref	Expression
sspwb	|- ( A C_ B <-> ~P A C_ ~P B )

Proof of Theorem sspwb

Dummy variable x is distinct from all other variables.

Step	Hyp	Ref	Expression
1		sstr2 3135	. . . . 5 |- ( x C_ A -> ( A C_ B -> x C_ B ) )
2	1	com12 30	. . . 4 |- ( A C_ B -> ( x C_ A -> x C_ B ) )
3		vex 2715	. . . . 5 |- x e. _V
4	3	elpw 3549	. . . 4 |- ( x e. ~P A <-> x C_ A )
5	3	elpw 3549	. . . 4 |- ( x e. ~P B <-> x C_ B )
6	2, 4, 5	3imtr4g 204	. . 3 |- ( A C_ B -> ( x e. ~P A -> x e. ~P B ) )
7	6	ssrdv 3134	. 2 |- ( A C_ B -> ~P A C_ ~P B )
8		ssel 3122	. . . 4 |- ( ~P A C_ ~P B -> ( { x } e. ~P A -> { x } e. ~P B ) )
9	3	snex 4146	. . . . . 6 |- { x } e. _V
10	9	elpw 3549	. . . . 5 |- ( { x } e. ~P A <-> { x } C_ A )
11	3	snss 3685	. . . . 5 |- ( x e. A <-> { x } C_ A )
12	10, 11	bitr4i 186	. . . 4 |- ( { x } e. ~P A <-> x e. A )
13	9	elpw 3549	. . . . 5 |- ( { x } e. ~P B <-> { x } C_ B )
14	3	snss 3685	. . . . 5 |- ( x e. B <-> { x } C_ B )
15	13, 14	bitr4i 186	. . . 4 |- ( { x } e. ~P B <-> x e. B )
16	8, 12, 15	3imtr3g 203	. . 3 |- ( ~P A C_ ~P B -> ( x e. A -> x e. B ) )
17	16	ssrdv 3134	. 2 |- ( ~P A C_ ~P B -> A C_ B )
18	7, 17	impbii 125	1 |- ( A C_ B <-> ~P A C_ ~P B )

Syntax hints:   <-> wb 104   e. wcel 2128   C_ wss 3102   ~Pcpw 3543   {csn 3560

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 699  ax-5 1427  ax-7 1428  ax-gen 1429  ax-ie1 1473  ax-ie2 1474  ax-8 1484  ax-10 1485  ax-11 1486  ax-i12 1487  ax-bndl 1489  ax-4 1490  ax-17 1506  ax-i9 1510  ax-ial 1514  ax-i5r 1515  ax-14 2131  ax-ext 2139  ax-sep 4082  ax-pow 4135

This theorem depends on definitions:  df-bi 116  df-tru 1338  df-nf 1441  df-sb 1743  df-clab 2144  df-cleq 2150  df-clel 2153  df-nfc 2288  df-v 2714  df-in 3108  df-ss 3115  df-pw 3545  df-sn 3566

This theorem is referenced by:  pwel  4178  ssextss  4180  pweqb  4183  fiss  6918  pw1on  7155  ntrss  12490