Theorem ssiun2s 4010

Description: Subset relationship for an indexed union. (Contributed by NM, 26-Oct-2003.)

Hypothesis

Ref	Expression
ssiun2s.1	|- (x = C -> B = D)

Assertion

Ref	Expression
ssiun2s	|- (C e. A -> D C_ U_x e. A B)

Distinct variable groups:   x,A   x,C   x,D

Allowed substitution hint:   B(x)

Proof of Theorem ssiun2s

Step	Hyp	Ref	Expression
1		nfcv 2489	. 2 |- F/_xC
2		nfcv 2489	. . 3 |- F/_xD
3		nfiu1 3997	. . 3 |- F/_xU_x e. A B
4	2, 3	nfss 3266	. 2 |- F/x D C_ U_x e. A B
5		ssiun2s.1	. . 3 |- (x = C -> B = D)
6	5	sseq1d 3298	. 2 |- (x = C -> (B C_ U_x e. A B <-> D C_ U_x e. A B))
7		ssiun2 4009	. 2 |- (x e. A -> B C_ U_x e. A B)
8	1, 4, 6, 7	vtoclgaf 2919	1 |- (C e. A -> D C_ U_x e. A B)

Syntax hints:   -> wi 4   = wceq 1642   e. wcel 1710   C_ wss 3257  U_ciun 3969

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1925  ax-ext 2334

This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-nan 1288  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649  df-clab 2340  df-cleq 2346  df-clel 2349  df-nfc 2478  df-ral 2619  df-rex 2620  df-v 2861  df-nin 3211  df-compl 3212  df-in 3213  df-ss 3259  df-iun 3971

This theorem is referenced by: (None)