Metamath Proof Explorer


Theorem lsmass

Description: Subgroup sum is associative. (Contributed by NM, 2-Mar-2014) (Revised by Mario Carneiro, 19-Apr-2016)

Ref Expression
Hypothesis lsmub1.p = ( LSSum ‘ 𝐺 )
Assertion lsmass ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( ( 𝑅 𝑇 ) 𝑈 ) = ( 𝑅 ( 𝑇 𝑈 ) ) )

Proof

Step Hyp Ref Expression
1 lsmub1.p = ( LSSum ‘ 𝐺 )
2 eqid ( Base ‘ 𝐺 ) = ( Base ‘ 𝐺 )
3 eqid ( +g𝐺 ) = ( +g𝐺 )
4 2 3 1 lsmval ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ) → ( 𝑅 𝑇 ) = ran ( 𝑎𝑅 , 𝑏𝑇 ↦ ( 𝑎 ( +g𝐺 ) 𝑏 ) ) )
5 4 3adant3 ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( 𝑅 𝑇 ) = ran ( 𝑎𝑅 , 𝑏𝑇 ↦ ( 𝑎 ( +g𝐺 ) 𝑏 ) ) )
6 5 rexeqdv ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( ∃ 𝑦 ∈ ( 𝑅 𝑇 ) ∃ 𝑐𝑈 𝑥 = ( 𝑦 ( +g𝐺 ) 𝑐 ) ↔ ∃ 𝑦 ∈ ran ( 𝑎𝑅 , 𝑏𝑇 ↦ ( 𝑎 ( +g𝐺 ) 𝑏 ) ) ∃ 𝑐𝑈 𝑥 = ( 𝑦 ( +g𝐺 ) 𝑐 ) ) )
7 ovex ( 𝑎 ( +g𝐺 ) 𝑏 ) ∈ V
8 7 rgen2w 𝑎𝑅𝑏𝑇 ( 𝑎 ( +g𝐺 ) 𝑏 ) ∈ V
9 eqid ( 𝑎𝑅 , 𝑏𝑇 ↦ ( 𝑎 ( +g𝐺 ) 𝑏 ) ) = ( 𝑎𝑅 , 𝑏𝑇 ↦ ( 𝑎 ( +g𝐺 ) 𝑏 ) )
10 oveq1 ( 𝑦 = ( 𝑎 ( +g𝐺 ) 𝑏 ) → ( 𝑦 ( +g𝐺 ) 𝑐 ) = ( ( 𝑎 ( +g𝐺 ) 𝑏 ) ( +g𝐺 ) 𝑐 ) )
11 10 eqeq2d ( 𝑦 = ( 𝑎 ( +g𝐺 ) 𝑏 ) → ( 𝑥 = ( 𝑦 ( +g𝐺 ) 𝑐 ) ↔ 𝑥 = ( ( 𝑎 ( +g𝐺 ) 𝑏 ) ( +g𝐺 ) 𝑐 ) ) )
12 11 rexbidv ( 𝑦 = ( 𝑎 ( +g𝐺 ) 𝑏 ) → ( ∃ 𝑐𝑈 𝑥 = ( 𝑦 ( +g𝐺 ) 𝑐 ) ↔ ∃ 𝑐𝑈 𝑥 = ( ( 𝑎 ( +g𝐺 ) 𝑏 ) ( +g𝐺 ) 𝑐 ) ) )
13 9 12 rexrnmpo ( ∀ 𝑎𝑅𝑏𝑇 ( 𝑎 ( +g𝐺 ) 𝑏 ) ∈ V → ( ∃ 𝑦 ∈ ran ( 𝑎𝑅 , 𝑏𝑇 ↦ ( 𝑎 ( +g𝐺 ) 𝑏 ) ) ∃ 𝑐𝑈 𝑥 = ( 𝑦 ( +g𝐺 ) 𝑐 ) ↔ ∃ 𝑎𝑅𝑏𝑇𝑐𝑈 𝑥 = ( ( 𝑎 ( +g𝐺 ) 𝑏 ) ( +g𝐺 ) 𝑐 ) ) )
14 8 13 ax-mp ( ∃ 𝑦 ∈ ran ( 𝑎𝑅 , 𝑏𝑇 ↦ ( 𝑎 ( +g𝐺 ) 𝑏 ) ) ∃ 𝑐𝑈 𝑥 = ( 𝑦 ( +g𝐺 ) 𝑐 ) ↔ ∃ 𝑎𝑅𝑏𝑇𝑐𝑈 𝑥 = ( ( 𝑎 ( +g𝐺 ) 𝑏 ) ( +g𝐺 ) 𝑐 ) )
15 6 14 bitrdi ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( ∃ 𝑦 ∈ ( 𝑅 𝑇 ) ∃ 𝑐𝑈 𝑥 = ( 𝑦 ( +g𝐺 ) 𝑐 ) ↔ ∃ 𝑎𝑅𝑏𝑇𝑐𝑈 𝑥 = ( ( 𝑎 ( +g𝐺 ) 𝑏 ) ( +g𝐺 ) 𝑐 ) ) )
16 2 3 1 lsmval ( ( 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( 𝑇 𝑈 ) = ran ( 𝑏𝑇 , 𝑐𝑈 ↦ ( 𝑏 ( +g𝐺 ) 𝑐 ) ) )
17 16 3adant1 ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( 𝑇 𝑈 ) = ran ( 𝑏𝑇 , 𝑐𝑈 ↦ ( 𝑏 ( +g𝐺 ) 𝑐 ) ) )
18 17 rexeqdv ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( ∃ 𝑧 ∈ ( 𝑇 𝑈 ) 𝑥 = ( 𝑎 ( +g𝐺 ) 𝑧 ) ↔ ∃ 𝑧 ∈ ran ( 𝑏𝑇 , 𝑐𝑈 ↦ ( 𝑏 ( +g𝐺 ) 𝑐 ) ) 𝑥 = ( 𝑎 ( +g𝐺 ) 𝑧 ) ) )
19 ovex ( 𝑏 ( +g𝐺 ) 𝑐 ) ∈ V
20 19 rgen2w 𝑏𝑇𝑐𝑈 ( 𝑏 ( +g𝐺 ) 𝑐 ) ∈ V
21 eqid ( 𝑏𝑇 , 𝑐𝑈 ↦ ( 𝑏 ( +g𝐺 ) 𝑐 ) ) = ( 𝑏𝑇 , 𝑐𝑈 ↦ ( 𝑏 ( +g𝐺 ) 𝑐 ) )
22 oveq2 ( 𝑧 = ( 𝑏 ( +g𝐺 ) 𝑐 ) → ( 𝑎 ( +g𝐺 ) 𝑧 ) = ( 𝑎 ( +g𝐺 ) ( 𝑏 ( +g𝐺 ) 𝑐 ) ) )
23 22 eqeq2d ( 𝑧 = ( 𝑏 ( +g𝐺 ) 𝑐 ) → ( 𝑥 = ( 𝑎 ( +g𝐺 ) 𝑧 ) ↔ 𝑥 = ( 𝑎 ( +g𝐺 ) ( 𝑏 ( +g𝐺 ) 𝑐 ) ) ) )
24 21 23 rexrnmpo ( ∀ 𝑏𝑇𝑐𝑈 ( 𝑏 ( +g𝐺 ) 𝑐 ) ∈ V → ( ∃ 𝑧 ∈ ran ( 𝑏𝑇 , 𝑐𝑈 ↦ ( 𝑏 ( +g𝐺 ) 𝑐 ) ) 𝑥 = ( 𝑎 ( +g𝐺 ) 𝑧 ) ↔ ∃ 𝑏𝑇𝑐𝑈 𝑥 = ( 𝑎 ( +g𝐺 ) ( 𝑏 ( +g𝐺 ) 𝑐 ) ) ) )
25 20 24 ax-mp ( ∃ 𝑧 ∈ ran ( 𝑏𝑇 , 𝑐𝑈 ↦ ( 𝑏 ( +g𝐺 ) 𝑐 ) ) 𝑥 = ( 𝑎 ( +g𝐺 ) 𝑧 ) ↔ ∃ 𝑏𝑇𝑐𝑈 𝑥 = ( 𝑎 ( +g𝐺 ) ( 𝑏 ( +g𝐺 ) 𝑐 ) ) )
26 18 25 bitrdi ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( ∃ 𝑧 ∈ ( 𝑇 𝑈 ) 𝑥 = ( 𝑎 ( +g𝐺 ) 𝑧 ) ↔ ∃ 𝑏𝑇𝑐𝑈 𝑥 = ( 𝑎 ( +g𝐺 ) ( 𝑏 ( +g𝐺 ) 𝑐 ) ) ) )
27 26 adantr ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) → ( ∃ 𝑧 ∈ ( 𝑇 𝑈 ) 𝑥 = ( 𝑎 ( +g𝐺 ) 𝑧 ) ↔ ∃ 𝑏𝑇𝑐𝑈 𝑥 = ( 𝑎 ( +g𝐺 ) ( 𝑏 ( +g𝐺 ) 𝑐 ) ) ) )
28 subgrcl ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) → 𝐺 ∈ Grp )
29 28 3ad2ant1 ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → 𝐺 ∈ Grp )
30 29 ad2antrr ( ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) ∧ ( 𝑏𝑇𝑐𝑈 ) ) → 𝐺 ∈ Grp )
31 2 subgss ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) → 𝑅 ⊆ ( Base ‘ 𝐺 ) )
32 31 3ad2ant1 ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → 𝑅 ⊆ ( Base ‘ 𝐺 ) )
33 32 ad2antrr ( ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) ∧ ( 𝑏𝑇𝑐𝑈 ) ) → 𝑅 ⊆ ( Base ‘ 𝐺 ) )
34 simplr ( ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) ∧ ( 𝑏𝑇𝑐𝑈 ) ) → 𝑎𝑅 )
35 33 34 sseldd ( ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) ∧ ( 𝑏𝑇𝑐𝑈 ) ) → 𝑎 ∈ ( Base ‘ 𝐺 ) )
36 2 subgss ( 𝑇 ∈ ( SubGrp ‘ 𝐺 ) → 𝑇 ⊆ ( Base ‘ 𝐺 ) )
37 36 3ad2ant2 ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → 𝑇 ⊆ ( Base ‘ 𝐺 ) )
38 37 ad2antrr ( ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) ∧ ( 𝑏𝑇𝑐𝑈 ) ) → 𝑇 ⊆ ( Base ‘ 𝐺 ) )
39 simprl ( ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) ∧ ( 𝑏𝑇𝑐𝑈 ) ) → 𝑏𝑇 )
40 38 39 sseldd ( ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) ∧ ( 𝑏𝑇𝑐𝑈 ) ) → 𝑏 ∈ ( Base ‘ 𝐺 ) )
41 2 subgss ( 𝑈 ∈ ( SubGrp ‘ 𝐺 ) → 𝑈 ⊆ ( Base ‘ 𝐺 ) )
42 41 3ad2ant3 ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → 𝑈 ⊆ ( Base ‘ 𝐺 ) )
43 42 ad2antrr ( ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) ∧ ( 𝑏𝑇𝑐𝑈 ) ) → 𝑈 ⊆ ( Base ‘ 𝐺 ) )
44 simprr ( ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) ∧ ( 𝑏𝑇𝑐𝑈 ) ) → 𝑐𝑈 )
45 43 44 sseldd ( ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) ∧ ( 𝑏𝑇𝑐𝑈 ) ) → 𝑐 ∈ ( Base ‘ 𝐺 ) )
46 2 3 grpass ( ( 𝐺 ∈ Grp ∧ ( 𝑎 ∈ ( Base ‘ 𝐺 ) ∧ 𝑏 ∈ ( Base ‘ 𝐺 ) ∧ 𝑐 ∈ ( Base ‘ 𝐺 ) ) ) → ( ( 𝑎 ( +g𝐺 ) 𝑏 ) ( +g𝐺 ) 𝑐 ) = ( 𝑎 ( +g𝐺 ) ( 𝑏 ( +g𝐺 ) 𝑐 ) ) )
47 30 35 40 45 46 syl13anc ( ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) ∧ ( 𝑏𝑇𝑐𝑈 ) ) → ( ( 𝑎 ( +g𝐺 ) 𝑏 ) ( +g𝐺 ) 𝑐 ) = ( 𝑎 ( +g𝐺 ) ( 𝑏 ( +g𝐺 ) 𝑐 ) ) )
48 47 eqeq2d ( ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) ∧ ( 𝑏𝑇𝑐𝑈 ) ) → ( 𝑥 = ( ( 𝑎 ( +g𝐺 ) 𝑏 ) ( +g𝐺 ) 𝑐 ) ↔ 𝑥 = ( 𝑎 ( +g𝐺 ) ( 𝑏 ( +g𝐺 ) 𝑐 ) ) ) )
49 48 2rexbidva ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) → ( ∃ 𝑏𝑇𝑐𝑈 𝑥 = ( ( 𝑎 ( +g𝐺 ) 𝑏 ) ( +g𝐺 ) 𝑐 ) ↔ ∃ 𝑏𝑇𝑐𝑈 𝑥 = ( 𝑎 ( +g𝐺 ) ( 𝑏 ( +g𝐺 ) 𝑐 ) ) ) )
50 27 49 bitr4d ( ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) ∧ 𝑎𝑅 ) → ( ∃ 𝑧 ∈ ( 𝑇 𝑈 ) 𝑥 = ( 𝑎 ( +g𝐺 ) 𝑧 ) ↔ ∃ 𝑏𝑇𝑐𝑈 𝑥 = ( ( 𝑎 ( +g𝐺 ) 𝑏 ) ( +g𝐺 ) 𝑐 ) ) )
51 50 rexbidva ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( ∃ 𝑎𝑅𝑧 ∈ ( 𝑇 𝑈 ) 𝑥 = ( 𝑎 ( +g𝐺 ) 𝑧 ) ↔ ∃ 𝑎𝑅𝑏𝑇𝑐𝑈 𝑥 = ( ( 𝑎 ( +g𝐺 ) 𝑏 ) ( +g𝐺 ) 𝑐 ) ) )
52 15 51 bitr4d ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( ∃ 𝑦 ∈ ( 𝑅 𝑇 ) ∃ 𝑐𝑈 𝑥 = ( 𝑦 ( +g𝐺 ) 𝑐 ) ↔ ∃ 𝑎𝑅𝑧 ∈ ( 𝑇 𝑈 ) 𝑥 = ( 𝑎 ( +g𝐺 ) 𝑧 ) ) )
53 grpmnd ( 𝐺 ∈ Grp → 𝐺 ∈ Mnd )
54 29 53 syl ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → 𝐺 ∈ Mnd )
55 2 1 lsmssv ( ( 𝐺 ∈ Mnd ∧ 𝑅 ⊆ ( Base ‘ 𝐺 ) ∧ 𝑇 ⊆ ( Base ‘ 𝐺 ) ) → ( 𝑅 𝑇 ) ⊆ ( Base ‘ 𝐺 ) )
56 54 32 37 55 syl3anc ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( 𝑅 𝑇 ) ⊆ ( Base ‘ 𝐺 ) )
57 2 3 1 lsmelvalx ( ( 𝐺 ∈ Grp ∧ ( 𝑅 𝑇 ) ⊆ ( Base ‘ 𝐺 ) ∧ 𝑈 ⊆ ( Base ‘ 𝐺 ) ) → ( 𝑥 ∈ ( ( 𝑅 𝑇 ) 𝑈 ) ↔ ∃ 𝑦 ∈ ( 𝑅 𝑇 ) ∃ 𝑐𝑈 𝑥 = ( 𝑦 ( +g𝐺 ) 𝑐 ) ) )
58 29 56 42 57 syl3anc ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( 𝑥 ∈ ( ( 𝑅 𝑇 ) 𝑈 ) ↔ ∃ 𝑦 ∈ ( 𝑅 𝑇 ) ∃ 𝑐𝑈 𝑥 = ( 𝑦 ( +g𝐺 ) 𝑐 ) ) )
59 2 1 lsmssv ( ( 𝐺 ∈ Mnd ∧ 𝑇 ⊆ ( Base ‘ 𝐺 ) ∧ 𝑈 ⊆ ( Base ‘ 𝐺 ) ) → ( 𝑇 𝑈 ) ⊆ ( Base ‘ 𝐺 ) )
60 54 37 42 59 syl3anc ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( 𝑇 𝑈 ) ⊆ ( Base ‘ 𝐺 ) )
61 2 3 1 lsmelvalx ( ( 𝐺 ∈ Grp ∧ 𝑅 ⊆ ( Base ‘ 𝐺 ) ∧ ( 𝑇 𝑈 ) ⊆ ( Base ‘ 𝐺 ) ) → ( 𝑥 ∈ ( 𝑅 ( 𝑇 𝑈 ) ) ↔ ∃ 𝑎𝑅𝑧 ∈ ( 𝑇 𝑈 ) 𝑥 = ( 𝑎 ( +g𝐺 ) 𝑧 ) ) )
62 29 32 60 61 syl3anc ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( 𝑥 ∈ ( 𝑅 ( 𝑇 𝑈 ) ) ↔ ∃ 𝑎𝑅𝑧 ∈ ( 𝑇 𝑈 ) 𝑥 = ( 𝑎 ( +g𝐺 ) 𝑧 ) ) )
63 52 58 62 3bitr4d ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( 𝑥 ∈ ( ( 𝑅 𝑇 ) 𝑈 ) ↔ 𝑥 ∈ ( 𝑅 ( 𝑇 𝑈 ) ) ) )
64 63 eqrdv ( ( 𝑅 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑇 ∈ ( SubGrp ‘ 𝐺 ) ∧ 𝑈 ∈ ( SubGrp ‘ 𝐺 ) ) → ( ( 𝑅 𝑇 ) 𝑈 ) = ( 𝑅 ( 𝑇 𝑈 ) ) )