Theorem in4 3338

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 3333	. . 3 |- ( B i^i ( C i^i D ) ) = ( C i^i ( B i^i D ) )
2	1	ineq2i 3320	. 2 |- ( A i^i ( B i^i ( C i^i D ) ) ) = ( A i^i ( C i^i ( B i^i D ) ) )
3		inass 3332	. 2 |- ( ( A i^i B ) i^i ( C i^i D ) ) = ( A i^i ( B i^i ( C i^i D ) ) )
4		inass 3332	. 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 2196	1 |- ( ( A i^i B ) i^i ( C i^i D ) ) = ( ( A i^i C ) i^i ( B i^i D ) )

Syntax hints:   = wceq 1343   i^i cin 3115

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-io 699  ax-5 1435  ax-7 1436  ax-gen 1437  ax-ie1 1481  ax-ie2 1482  ax-8 1492  ax-10 1493  ax-11 1494  ax-i12 1495  ax-bndl 1497  ax-4 1498  ax-17 1514  ax-i9 1518  ax-ial 1522  ax-i5r 1523  ax-ext 2147

This theorem depends on definitions:  df-bi 116  df-tru 1346  df-nf 1449  df-sb 1751  df-clab 2152  df-cleq 2158  df-clel 2161  df-nfc 2297  df-v 2728  df-in 3122

This theorem is referenced by:  inindi  3339  inindir  3340