Theorem dif0 3535

Description: The difference between a class and the empty set. Part of Exercise 4.4 of [Stoll] p. 16. (Contributed by NM, 17-Aug-2004.)

Assertion

Ref	Expression
dif0	⊢ (𝐴 ∖ ∅) = 𝐴

Proof of Theorem dif0

Step	Hyp	Ref	Expression
1		difid 3533	. . 3 ⊢ (𝐴 ∖ 𝐴) = ∅
2	1	difeq2i 3292	. 2 ⊢ (𝐴 ∖ (𝐴 ∖ 𝐴)) = (𝐴 ∖ ∅)
3		difdif 3302	. 2 ⊢ (𝐴 ∖ (𝐴 ∖ 𝐴)) = 𝐴
4	2, 3	eqtr3i 2229	1 ⊢ (𝐴 ∖ ∅) = 𝐴

Syntax hints:   = wceq 1373   ∖ cdif 3167  ∅c0 3464

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 615  ax-in2 616  ax-io 711  ax-5 1471  ax-7 1472  ax-gen 1473  ax-ie1 1517  ax-ie2 1518  ax-8 1528  ax-10 1529  ax-11 1530  ax-i12 1531  ax-bndl 1533  ax-4 1534  ax-17 1550  ax-i9 1554  ax-ial 1558  ax-i5r 1559  ax-ext 2188

This theorem depends on definitions:  df-bi 117  df-tru 1376  df-nf 1485  df-sb 1787  df-clab 2193  df-cleq 2199  df-clel 2202  df-nfc 2338  df-ral 2490  df-rab 2494  df-v 2775  df-dif 3172  df-in 3176  df-ss 3183  df-nul 3465

This theorem is referenced by:  disjdif2  3543  exmid1stab  4259  2oconcl  6537  diffifi  7005  undifdc  7035  difinfinf  7217  ismkvnex  7271  m1bits  12341  0cld  14654