Theorem dif0 2339

Description: The difference between a class and the empty set. Part of Exercise 4.4 of [Stoll] p. 16.

Assertion

Ref	Expression
dif0	|- (A \ (/)) = A

Proof of Theorem dif0

Step	Hyp	Ref	Expression
1		difid 2338	. . 3 |- (A \ A) = (/)
2	1	difeq2i 2159	. 2 |- (A \ (A \ A)) = (A \ (/))
3		difdif 2169	. 2 |- (A \ (A \ A)) = A
4	2, 3	eqtr3 1500	1 |- (A \ (/)) = A

Syntax hints:   = wceq 958   \ cdif 2047  (/)c0 2283

This theorem is referenced by:  undifv 2343  oe0m0 4165  oev2 4168  0cld 7675  rcfpfillem3 10565

This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7  ax-7 964  ax-gen 965  ax-8 966  ax-10 968  ax-12 970  ax-17 973  ax-4 975  ax-5o 977  ax-6o 980  ax-9o 1125  ax-10o 1142  ax-16 1212  ax-11o 1220  ax-ext 1462

This theorem depends on definitions:  df-bi 147  df-or 224  df-an 225  df-ex 983  df-sb 1174  df-clab 1467  df-cleq 1472  df-clel 1475  df-ne 1590  df-v 1815  df-dif 2052  df-in 2054  df-ss 2056  df-nul 2284

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