Theorem in4 3472

Description: Rearrangement of intersection of 4 classes. (Contributed by NM, 21-Apr-2001.)

Assertion

Ref	Expression
in4	|- ((A i^i B) i^i (C i^i D)) = ((A i^i C) i^i (B i^i D))

Proof of Theorem in4

Step	Hyp	Ref	Expression
1		in12 3467	. . 3 |- (B i^i (C i^i D)) = (C i^i (B i^i D))
2	1	ineq2i 3455	. 2 |- (A i^i (B i^i (C i^i D))) = (A i^i (C i^i (B i^i D)))
3		inass 3466	. 2 |- ((A i^i B) i^i (C i^i D)) = (A i^i (B i^i (C i^i D)))
4		inass 3466	. 2 |- ((A i^i C) i^i (B i^i D)) = (A i^i (C i^i (B i^i D)))
5	2, 3, 4	3eqtr4i 2383	1 |- ((A i^i B) i^i (C i^i D)) = ((A i^i C) i^i (B i^i D))

Syntax hints:   = wceq 1642   i^i cin 3209

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

This theorem is referenced by:  inindi  3473  inindir  3474