Theorem difeq2 3321

Description: Equality theorem for class difference. (Contributed by NM, 10-Feb-1997.) (Proof shortened by Andrew Salmon, 26-Jun-2011.)

Assertion

Ref	Expression
difeq2	|- ( A = B -> ( C \ A ) = ( C \ B ) )

Proof of Theorem difeq2

Dummy variable x is distinct from all other variables.

Step	Hyp	Ref	Expression
1		eleq2 2295	. . . 4 |- ( A = B -> ( x e. A <-> x e. B ) )
2	1	notbid 673	. . 3 |- ( A = B -> ( -. x e. A <-> -. x e. B ) )
3	2	rabbidv 2792	. 2 |- ( A = B -> { x e. C | -. x e. A } = { x e. C | -. x e. B } )
4		dfdif2 3209	. 2 |- ( C \ A ) = { x e. C | -. x e. A }
5		dfdif2 3209	. 2 |- ( C \ B ) = { x e. C | -. x e. B }
6	3, 4, 5	3eqtr4g 2289	1 |- ( A = B -> ( C \ A ) = ( C \ B ) )

Syntax hints:   -. wn 3   -> wi 4   = wceq 1398   e. wcel 2202   {crab 2515   \ cdif 3198

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 619  ax-in2 620  ax-5 1496  ax-7 1497  ax-gen 1498  ax-ie1 1542  ax-ie2 1543  ax-8 1553  ax-11 1555  ax-4 1559  ax-17 1575  ax-i9 1579  ax-ial 1583  ax-i5r 1584  ax-ext 2213

This theorem depends on definitions:  df-bi 117  df-tru 1401  df-nf 1510  df-sb 1811  df-clab 2218  df-cleq 2224  df-clel 2227  df-ral 2516  df-rab 2520  df-dif 3203

This theorem is referenced by:  difeq12  3322  difeq2i  3324  difeq2d  3327  disjdif2  3575  ssdifeq0  3579  2oconcl  6650  diffitest  7119  diffifi  7126  undifdc  7159  sbthlem2  7200  isbth  7209  difinfinf  7360  ismkvnex  7414  iscld  14914