Theorem unidif 4196

Description: If the difference A \ B contains the largest members of A, then the union of the difference is the union of A. (Contributed by NM, 22-Mar-2004.)

Assertion

Ref	Expression
unidif	|- ( A. x e. A E. y e. ( A \ B ) x C_ y -> U. ( A \ B ) = U. A )

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

Proof of Theorem unidif

Step	Hyp	Ref	Expression
1		uniss2 4195	. . 3 |- ( A. x e. A E. y e. ( A \ B ) x C_ y -> U. A C_ U. ( A \ B ) )
2		difss 3545	. . . 4 |- ( A \ B ) C_ A
3	2	unissi 4186	. . 3 |- U. ( A \ B ) C_ U. A
4	1, 3	jctil 535	. 2 |- ( A. x e. A E. y e. ( A \ B ) x C_ y -> ( U. ( A \ B ) C_ U. A /\ U. A C_ U. ( A \ B ) ) )
5		eqss 3432	. 2 |- ( U. ( A \ B ) = U. A <-> ( U. ( A \ B ) C_ U. A /\ U. A C_ U. ( A \ B ) ) )
6	4, 5	sylibr 212	1 |- ( A. x e. A E. y e. ( A \ B ) x C_ y -> U. ( A \ B ) = U. A )

Syntax hints:   -> wi 4   /\ wa 367   = wceq 1399   A.wral 2732   E.wrex 2733   \ cdif 3386   C_ wss 3389   U.cuni 4163

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1626  ax-4 1639  ax-5 1712  ax-6 1755  ax-7 1798  ax-10 1845  ax-11 1850  ax-12 1862  ax-13 2006  ax-ext 2360

This theorem depends on definitions:  df-bi 185  df-an 369  df-tru 1402  df-ex 1621  df-nf 1625  df-sb 1748  df-clab 2368  df-cleq 2374  df-clel 2377  df-nfc 2532  df-ral 2737  df-rex 2738  df-v 3036  df-dif 3392  df-in 3396  df-ss 3403  df-uni 4164

This theorem is referenced by:  ordunidif  4840