Theorem difid 3563

Description: The difference between a class and itself is the empty set. Proposition 5.15 of [TakeutiZaring] p. 20. Also Theorem 32 of [Suppes] p. 28. (Contributed by NM, 22-Apr-2004.)

Assertion

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

Proof of Theorem difid

Step	Hyp	Ref	Expression
1		ssid 3247	. 2 |- A C_ A
2		ssdif0im 3559	. 2 |- ( A C_ A -> ( A \ A ) = (/) )
3	1, 2	ax-mp 5	1 |- ( A \ A ) = (/)

Syntax hints:   = wceq 1397   \ cdif 3197   C_ wss 3200   (/)c0 3494

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-io 716  ax-5 1495  ax-7 1496  ax-gen 1497  ax-ie1 1541  ax-ie2 1542  ax-8 1552  ax-10 1553  ax-11 1554  ax-i12 1555  ax-bndl 1557  ax-4 1558  ax-17 1574  ax-i9 1578  ax-ial 1582  ax-i5r 1583  ax-ext 2213

This theorem depends on definitions:  df-bi 117  df-tru 1400  df-nf 1509  df-sb 1811  df-clab 2218  df-cleq 2224  df-clel 2227  df-nfc 2363  df-v 2804  df-dif 3202  df-in 3206  df-ss 3213  df-nul 3495

This theorem is referenced by:  dif0  3565  difun2  3574  diftpsn3  3814  2oconcl  6606  ismkvnex  7353  topcld  14832