Theorem iunxdif2 4015

Description: Indexed union with a class difference as its index. (Contributed by NM, 10-Dec-2004.)

Hypothesis

Ref	Expression
iunxdif2.1	|- (x = y -> C = D)

Assertion

Ref	Expression
iunxdif2	|- (A.x e. A E.y e. (A \ B)C C_ D -> U_y e. (A \ B)D = U_x e. A C)

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

Allowed substitution hints:   C(x)   D(y)

Proof of Theorem iunxdif2

Step	Hyp	Ref	Expression
1		iunss2 4012	. . 3 |- (A.x e. A E.y e. (A \ B)C C_ D -> U_x e. A C C_ U_y e. (A \ B)D)
2		difss 3394	. . . . 5 |- (A \ B) C_ A
3		iunss1 3981	. . . . 5 |- ((A \ B) C_ A -> U_y e. (A \ B)D C_ U_y e. A D)
4	2, 3	ax-mp 5	. . . 4 |- U_y e. (A \ B)D C_ U_y e. A D
5		iunxdif2.1	. . . . 5 |- (x = y -> C = D)
6	5	cbviunv 4006	. . . 4 |- U_x e. A C = U_y e. A D
7	4, 6	sseqtr4i 3305	. . 3 |- U_y e. (A \ B)D C_ U_x e. A C
8	1, 7	jctil 523	. 2 |- (A.x e. A E.y e. (A \ B)C C_ D -> (U_y e. (A \ B)D C_ U_x e. A C /\ U_x e. A C C_ U_y e. (A \ B)D))
9		eqss 3288	. 2 |- (U_y e. (A \ B)D = U_x e. A C <-> (U_y e. (A \ B)D C_ U_x e. A C /\ U_x e. A C C_ U_y e. (A \ B)D))
10	8, 9	sylibr 203	1 |- (A.x e. A E.y e. (A \ B)C C_ D -> U_y e. (A \ B)D = U_x e. A C)

Syntax hints:   -> wi 4   /\ wa 358   = wceq 1642  A.wral 2615  E.wrex 2616   \ cdif 3207   C_ wss 3258  U_ciun 3970

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 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 2479  df-ral 2620  df-rex 2621  df-v 2862  df-nin 3212  df-compl 3213  df-in 3214  df-dif 3216  df-ss 3260  df-iun 3972

This theorem is referenced by: (None)