Theorem csbun 4009

Description: Distribution of class substitution over union of two classes. (Contributed by Drahflow, 23-Sep-2015.) (Revised by Mario Carneiro, 11-Dec-2016.) (Revised by NM, 13-Sep-2018.)

Assertion

Ref	Expression
csbun	|- [_ A / x ]_ ( B u. C ) = ( [_ A / x ]_ B u. [_ A / x ]_ C )

Proof of Theorem csbun

Dummy variable y is distinct from all other variables.

Step	Hyp	Ref	Expression
1		csbeq1 3536	. . . 4 |- ( y = A -> [_ y / x ]_ ( B u. C ) = [_ A / x ]_ ( B u. C ) )
2		csbeq1 3536	. . . . 5 |- ( y = A -> [_ y / x ]_ B = [_ A / x ]_ B )
3		csbeq1 3536	. . . . 5 |- ( y = A -> [_ y / x ]_ C = [_ A / x ]_ C )
4	2, 3	uneq12d 3768	. . . 4 |- ( y = A -> ( [_ y / x ]_ B u. [_ y / x ]_ C ) = ( [_ A / x ]_ B u. [_ A / x ]_ C ) )
5	1, 4	eqeq12d 2637	. . 3 |- ( y = A -> ( [_ y / x ]_ ( B u. C ) = ( [_ y / x ]_ B u. [_ y / x ]_ C ) <-> [_ A / x ]_ ( B u. C ) = ( [_ A / x ]_ B u. [_ A / x ]_ C ) ) )
6		vex 3203	. . . 4 |- y e. _V
7		nfcsb1v 3549	. . . . 5 |- F/_ x [_ y / x ]_ B
8		nfcsb1v 3549	. . . . 5 |- F/_ x [_ y / x ]_ C
9	7, 8	nfun 3769	. . . 4 |- F/_ x ( [_ y / x ]_ B u. [_ y / x ]_ C )
10		csbeq1a 3542	. . . . 5 |- ( x = y -> B = [_ y / x ]_ B )
11		csbeq1a 3542	. . . . 5 |- ( x = y -> C = [_ y / x ]_ C )
12	10, 11	uneq12d 3768	. . . 4 |- ( x = y -> ( B u. C ) = ( [_ y / x ]_ B u. [_ y / x ]_ C ) )
13	6, 9, 12	csbief 3558	. . 3 |- [_ y / x ]_ ( B u. C ) = ( [_ y / x ]_ B u. [_ y / x ]_ C )
14	5, 13	vtoclg 3266	. 2 |- ( A e. _V -> [_ A / x ]_ ( B u. C ) = ( [_ A / x ]_ B u. [_ A / x ]_ C ) )
15		un0 3967	. . . 4 |- ( (/) u. (/) ) = (/)
16	15	a1i 11	. . 3 |- ( -. A e. _V -> ( (/) u. (/) ) = (/) )
17		csbprc 3980	. . . 4 |- ( -. A e. _V -> [_ A / x ]_ B = (/) )
18		csbprc 3980	. . . 4 |- ( -. A e. _V -> [_ A / x ]_ C = (/) )
19	17, 18	uneq12d 3768	. . 3 |- ( -. A e. _V -> ( [_ A / x ]_ B u. [_ A / x ]_ C ) = ( (/) u. (/) ) )
20		csbprc 3980	. . 3 |- ( -. A e. _V -> [_ A / x ]_ ( B u. C ) = (/) )
21	16, 19, 20	3eqtr4rd 2667	. 2 |- ( -. A e. _V -> [_ A / x ]_ ( B u. C ) = ( [_ A / x ]_ B u. [_ A / x ]_ C ) )
22	14, 21	pm2.61i 176	1 |- [_ A / x ]_ ( B u. C ) = ( [_ A / x ]_ B u. [_ A / x ]_ C )

Syntax hints:   -. wn 3   = wceq 1483   e. wcel 1990   _Vcvv 3200   [_csb 3533   u. cun 3572   (/)c0 3915

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737  ax-5 1839  ax-6 1888  ax-7 1935  ax-9 1999  ax-10 2019  ax-11 2034  ax-12 2047  ax-13 2246  ax-ext 2602

This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-3an 1039  df-tru 1486  df-fal 1489  df-ex 1705  df-nf 1710  df-sb 1881  df-clab 2609  df-cleq 2615  df-clel 2618  df-nfc 2753  df-v 3202  df-sbc 3436  df-csb 3534  df-dif 3577  df-un 3579  df-nul 3916

This theorem is referenced by:  csbprg  4244