Theorem disjss1 4256

Description: A subset of a disjoint collection is disjoint. (Contributed by Mario Carneiro, 14-Nov-2016.)

Assertion

Ref	Expression
disjss1	|- ( A C_ B -> (Disj x e. B C -> Disj x e. A C ) )

Distinct variable groups:   x, A   x, B

Allowed substitution hint:   C( x)

Proof of Theorem disjss1

Dummy variable y is distinct from all other variables.

Step	Hyp	Ref	Expression
1		ssel 3338	. . . . . 6 |- ( A C_ B -> ( x e. A -> x e. B ) )
2	1	anim1d 559	. . . . 5 |- ( A C_ B -> ( ( x e. A /\ y e. C ) -> ( x e. B /\ y e. C ) ) )
3	2	alrimiv 1684	. . . 4 |- ( A C_ B -> A. x ( ( x e. A /\ y e. C ) -> ( x e. B /\ y e. C ) ) )
4		moim 2316	. . . 4 |- ( A. x ( ( x e. A /\ y e. C ) -> ( x e. B /\ y e. C ) ) -> ( E* x ( x e. B /\ y e. C ) -> E* x ( x e. A /\ y e. C ) ) )
5	3, 4	syl 16	. . 3 |- ( A C_ B -> ( E* x ( x e. B /\ y e. C ) -> E* x ( x e. A /\ y e. C ) ) )
6	5	alimdv 1674	. 2 |- ( A C_ B -> ( A. y E* x ( x e. B /\ y e. C ) -> A. y E* x ( x e. A /\ y e. C ) ) )
7		dfdisj2 4252	. 2 |- (Disj x e. B C <-> A. y E* x ( x e. B /\ y e. C ) )
8		dfdisj2 4252	. 2 |- (Disj x e. A C <-> A. y E* x ( x e. A /\ y e. C ) )
9	6, 7, 8	3imtr4g 270	1 |- ( A C_ B -> (Disj x e. B C -> Disj x e. A C ) )

Syntax hints:   -> wi 4   /\ wa 369   A.wal 1360   e. wcel 1755   E*wmo 2255   C_ wss 3316  Disj wdisj 4250

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1594  ax-4 1605  ax-5 1669  ax-6 1707  ax-7 1727  ax-10 1774  ax-11 1779  ax-12 1791  ax-13 1942  ax-ext 2414

This theorem depends on definitions:  df-bi 185  df-an 371  df-ex 1590  df-nf 1593  df-sb 1700  df-eu 2258  df-mo 2259  df-clab 2420  df-cleq 2426  df-clel 2429  df-rmo 2713  df-in 3323  df-ss 3330  df-disj 4251

This theorem is referenced by:  disjeq1  4257  disjx0  4275  disjxiun  4277  disjss3  4279  volfiniun  20869  uniioovol  20900  uniioombllem4  20907  sibfof  26573