Metamath Proof Explorer


Theorem cdainflem

Description: Any partition of omega into two pieces (which may be disjoint) contains an infinite subset. (Contributed by Mario Carneiro, 11-Feb-2013)

Ref Expression
Assertion cdainflem
|- ( ( A u. B ) ~~ _om -> ( A ~~ _om \/ B ~~ _om ) )

Proof

Step Hyp Ref Expression
1 unfi2
 |-  ( ( A ~< _om /\ B ~< _om ) -> ( A u. B ) ~< _om )
2 sdomnen
 |-  ( ( A u. B ) ~< _om -> -. ( A u. B ) ~~ _om )
3 1 2 syl
 |-  ( ( A ~< _om /\ B ~< _om ) -> -. ( A u. B ) ~~ _om )
4 3 con2i
 |-  ( ( A u. B ) ~~ _om -> -. ( A ~< _om /\ B ~< _om ) )
5 ianor
 |-  ( -. ( A ~< _om /\ B ~< _om ) <-> ( -. A ~< _om \/ -. B ~< _om ) )
6 relen
 |-  Rel ~~
7 6 brrelex1i
 |-  ( ( A u. B ) ~~ _om -> ( A u. B ) e. _V )
8 ssun1
 |-  A C_ ( A u. B )
9 ssdomg
 |-  ( ( A u. B ) e. _V -> ( A C_ ( A u. B ) -> A ~<_ ( A u. B ) ) )
10 7 8 9 mpisyl
 |-  ( ( A u. B ) ~~ _om -> A ~<_ ( A u. B ) )
11 domentr
 |-  ( ( A ~<_ ( A u. B ) /\ ( A u. B ) ~~ _om ) -> A ~<_ _om )
12 10 11 mpancom
 |-  ( ( A u. B ) ~~ _om -> A ~<_ _om )
13 12 anim1i
 |-  ( ( ( A u. B ) ~~ _om /\ -. A ~< _om ) -> ( A ~<_ _om /\ -. A ~< _om ) )
14 bren2
 |-  ( A ~~ _om <-> ( A ~<_ _om /\ -. A ~< _om ) )
15 13 14 sylibr
 |-  ( ( ( A u. B ) ~~ _om /\ -. A ~< _om ) -> A ~~ _om )
16 15 ex
 |-  ( ( A u. B ) ~~ _om -> ( -. A ~< _om -> A ~~ _om ) )
17 ssun2
 |-  B C_ ( A u. B )
18 ssdomg
 |-  ( ( A u. B ) e. _V -> ( B C_ ( A u. B ) -> B ~<_ ( A u. B ) ) )
19 7 17 18 mpisyl
 |-  ( ( A u. B ) ~~ _om -> B ~<_ ( A u. B ) )
20 domentr
 |-  ( ( B ~<_ ( A u. B ) /\ ( A u. B ) ~~ _om ) -> B ~<_ _om )
21 19 20 mpancom
 |-  ( ( A u. B ) ~~ _om -> B ~<_ _om )
22 21 anim1i
 |-  ( ( ( A u. B ) ~~ _om /\ -. B ~< _om ) -> ( B ~<_ _om /\ -. B ~< _om ) )
23 bren2
 |-  ( B ~~ _om <-> ( B ~<_ _om /\ -. B ~< _om ) )
24 22 23 sylibr
 |-  ( ( ( A u. B ) ~~ _om /\ -. B ~< _om ) -> B ~~ _om )
25 24 ex
 |-  ( ( A u. B ) ~~ _om -> ( -. B ~< _om -> B ~~ _om ) )
26 16 25 orim12d
 |-  ( ( A u. B ) ~~ _om -> ( ( -. A ~< _om \/ -. B ~< _om ) -> ( A ~~ _om \/ B ~~ _om ) ) )
27 5 26 syl5bi
 |-  ( ( A u. B ) ~~ _om -> ( -. ( A ~< _om /\ B ~< _om ) -> ( A ~~ _om \/ B ~~ _om ) ) )
28 4 27 mpd
 |-  ( ( A u. B ) ~~ _om -> ( A ~~ _om \/ B ~~ _om ) )