Theorem inass 4169

Description: Associative law for intersection of classes. Exercise 9 of [TakeutiZaring] p. 17. (Contributed by NM, 3-May-1994.)

Assertion

Ref	Expression
inass	⊢ ((𝐴 ∩ 𝐵) ∩ 𝐶) = (𝐴 ∩ (𝐵 ∩ 𝐶))

Proof of Theorem inass

Dummy variable 𝑥 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		anass 468	. . . 4 ⊢ (((𝑥 ∈ 𝐴 ∧ 𝑥 ∈ 𝐵) ∧ 𝑥 ∈ 𝐶) ↔ (𝑥 ∈ 𝐴 ∧ (𝑥 ∈ 𝐵 ∧ 𝑥 ∈ 𝐶)))
2		elin 3906	. . . . 5 ⊢ (𝑥 ∈ (𝐵 ∩ 𝐶) ↔ (𝑥 ∈ 𝐵 ∧ 𝑥 ∈ 𝐶))
3	2	anbi2i 624	. . . 4 ⊢ ((𝑥 ∈ 𝐴 ∧ 𝑥 ∈ (𝐵 ∩ 𝐶)) ↔ (𝑥 ∈ 𝐴 ∧ (𝑥 ∈ 𝐵 ∧ 𝑥 ∈ 𝐶)))
4	1, 3	bitr4i 278	. . 3 ⊢ (((𝑥 ∈ 𝐴 ∧ 𝑥 ∈ 𝐵) ∧ 𝑥 ∈ 𝐶) ↔ (𝑥 ∈ 𝐴 ∧ 𝑥 ∈ (𝐵 ∩ 𝐶)))
5		elin 3906	. . . 4 ⊢ (𝑥 ∈ (𝐴 ∩ 𝐵) ↔ (𝑥 ∈ 𝐴 ∧ 𝑥 ∈ 𝐵))
6	5	anbi1i 625	. . 3 ⊢ ((𝑥 ∈ (𝐴 ∩ 𝐵) ∧ 𝑥 ∈ 𝐶) ↔ ((𝑥 ∈ 𝐴 ∧ 𝑥 ∈ 𝐵) ∧ 𝑥 ∈ 𝐶))
7		elin 3906	. . 3 ⊢ (𝑥 ∈ (𝐴 ∩ (𝐵 ∩ 𝐶)) ↔ (𝑥 ∈ 𝐴 ∧ 𝑥 ∈ (𝐵 ∩ 𝐶)))
8	4, 6, 7	3bitr4i 303	. 2 ⊢ ((𝑥 ∈ (𝐴 ∩ 𝐵) ∧ 𝑥 ∈ 𝐶) ↔ 𝑥 ∈ (𝐴 ∩ (𝐵 ∩ 𝐶)))
9	8	ineqri 4153	1 ⊢ ((𝐴 ∩ 𝐵) ∩ 𝐶) = (𝐴 ∩ (𝐵 ∩ 𝐶))

Syntax hints:   ∧ wa 395   = wceq 1542   ∈ wcel 2114   ∩ cin 3889

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1912  ax-6 1969  ax-7 2010  ax-8 2116  ax-9 2124  ax-ext 2709

This theorem depends on definitions:  df-bi 207  df-an 396  df-tru 1545  df-ex 1782  df-sb 2069  df-clab 2716  df-cleq 2729  df-clel 2812  df-v 3432  df-in 3897

This theorem is referenced by:  in12  4170  in32  4171  in4  4175  indif2  4222  difun1  4240  dfrab3ss  4264  dfif4  4483  resres  5958  inres  5963  imainrect  6146  cnvrescnv  6160  predidm  6291  onfr  6363  fresaun  6712  fresaunres2  6713  fimacnvinrn2  7025  epfrs  9652  incexclem  15801  sadeq  16441  smuval2  16451  smumul  16462  ressinbas  17215  ressress  17217  resscatc  18076  sylow2a  19594  ablfac1eu  20050  ressmplbas2  22005  restco  23129  restopnb  23140  kgeni  23502  hausdiag  23610  fclsrest  23989  clsocv  25217  itg2cnlem2  25729  rplogsum  27490  chjassi  31557  pjoml2i  31656  cmcmlem  31662  cmbr3i  31671  fh1  31689  fh2  31690  pj3lem1  32277  dmdbr5  32379  mdslmd3i  32403  mdexchi  32406  atabsi  32472  dmdbr6ati  32494  prsss  34060  inelcarsg  34455  carsgclctunlem1  34461  msrid  35727  dfttc4  36712  redundss3  39033  refrelsredund4  39037  dfpetparts2  39293  dfpeters2  39295  osumcllem9N  40410  dihmeetbclemN  41750  dihmeetlem11N  41763  wfac8prim  45429  inabs3  45487  uzinico2  45991  caragenuncllem  46940  resinsn  49341  restclsseplem  49384