Theorem sspss 3706

Description: Subclass in terms of proper subclass. (Contributed by NM, 25-Feb-1996.)

Assertion

Ref	Expression
sspss	|- ( A C_ B <-> ( A C. B \/ A = B ) )

Proof of Theorem sspss

Step	Hyp	Ref	Expression
1		dfpss2 3692	. . . . 5 |- ( A C. B <-> ( A C_ B /\ -. A = B ) )
2	1	simplbi2 655	. . . 4 |- ( A C_ B -> ( -. A = B -> A C. B ) )
3	2	con1d 139	. . 3 |- ( A C_ B -> ( -. A C. B -> A = B ) )
4	3	orrd 393	. 2 |- ( A C_ B -> ( A C. B \/ A = B ) )
5		pssss 3702	. . 3 |- ( A C. B -> A C_ B )
6		eqimss 3657	. . 3 |- ( A = B -> A C_ B )
7	5, 6	jaoi 394	. 2 |- ( ( A C. B \/ A = B ) -> A C_ B )
8	4, 7	impbii 199	1 |- ( A C_ B <-> ( A C. B \/ A = B ) )

Syntax hints:   -. wn 3   <-> wb 196   \/ wo 383   = wceq 1483   C_ wss 3574   C. wpss 3575

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-ne 2795  df-in 3581  df-ss 3588  df-pss 3590

This theorem is referenced by:  sspsstri  3709  sspsstr  3712  psssstr  3713  ordsseleq  5752  sorpssuni  6946  sorpssint  6947  ssnnfi  8179  ackbij1b  9061  fin23lem40  9173  zorng  9326  psslinpr  9853  suplem2pr  9875  ressval3d  15937  mrissmrcd  16300  pgpssslw  18029  pgpfac1lem5  18478  idnghm  22547  dfon2lem4  31691  finminlem  32312  lkrss2N  34456  dvh3dim3N  36738