Theorem int0 3941

Description: The intersection of the empty set is the universal class. Exercise 2 of [TakeutiZaring] p. 44. (Contributed by NM, 18-Aug-1993.)

Assertion

Ref	Expression
int0	|- |^|(/) = _V

Proof of Theorem int0

Dummy variables x y are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		noel 3555	. . . . . 6 |- -. y e. (/)
2	1	pm2.21i 123	. . . . 5 |- (y e. (/) -> x e. y)
3	2	ax-gen 1546	. . . 4 |- A.y(y e. (/) -> x e. y)
4		eqid 2353	. . . 4 |- x = x
5	3, 4	2th 230	. . 3 |- (A.y(y e. (/) -> x e. y) <-> x = x)
6	5	abbii 2466	. 2 |- {x | A.y(y e. (/) -> x e. y)} = {x | x = x}
7		df-int 3928	. 2 |- |^|(/) = {x | A.y(y e. (/) -> x e. y)}
8		df-v 2862	. 2 |- _V = {x | x = x}
9	6, 7, 8	3eqtr4i 2383	1 |- |^|(/) = _V

Syntax hints:   -> wi 4  A.wal 1540   = wceq 1642   e. wcel 1710  {cab 2339  _Vcvv 2860  (/)c0 3551  |^|cint 3927

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1925  ax-ext 2334

This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-nan 1288  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649  df-clab 2340  df-cleq 2346  df-clel 2349  df-nfc 2479  df-v 2862  df-nin 3212  df-compl 3213  df-in 3214  df-dif 3216  df-nul 3552  df-int 3928

This theorem is referenced by:  unissint  3951  uniintsn  3964  rint0  3967