Metamath Proof Explorer


Theorem grpinvadd

Description: The inverse of the group operation reverses the arguments. Lemma 2.2.1(d) of Herstein p. 55. (Contributed by NM, 27-Oct-2006)

Ref Expression
Hypotheses grpinvadd.b 𝐵 = ( Base ‘ 𝐺 )
grpinvadd.p + = ( +g𝐺 )
grpinvadd.n 𝑁 = ( invg𝐺 )
Assertion grpinvadd ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( 𝑁 ‘ ( 𝑋 + 𝑌 ) ) = ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) )

Proof

Step Hyp Ref Expression
1 grpinvadd.b 𝐵 = ( Base ‘ 𝐺 )
2 grpinvadd.p + = ( +g𝐺 )
3 grpinvadd.n 𝑁 = ( invg𝐺 )
4 simp1 ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → 𝐺 ∈ Grp )
5 simp2 ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → 𝑋𝐵 )
6 simp3 ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → 𝑌𝐵 )
7 1 3 grpinvcl ( ( 𝐺 ∈ Grp ∧ 𝑌𝐵 ) → ( 𝑁𝑌 ) ∈ 𝐵 )
8 7 3adant2 ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( 𝑁𝑌 ) ∈ 𝐵 )
9 1 3 grpinvcl ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵 ) → ( 𝑁𝑋 ) ∈ 𝐵 )
10 9 3adant3 ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( 𝑁𝑋 ) ∈ 𝐵 )
11 1 2 grpcl ( ( 𝐺 ∈ Grp ∧ ( 𝑁𝑌 ) ∈ 𝐵 ∧ ( 𝑁𝑋 ) ∈ 𝐵 ) → ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ∈ 𝐵 )
12 4 8 10 11 syl3anc ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ∈ 𝐵 )
13 1 2 grpass ( ( 𝐺 ∈ Grp ∧ ( 𝑋𝐵𝑌𝐵 ∧ ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ∈ 𝐵 ) ) → ( ( 𝑋 + 𝑌 ) + ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ) = ( 𝑋 + ( 𝑌 + ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ) ) )
14 4 5 6 12 13 syl13anc ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( ( 𝑋 + 𝑌 ) + ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ) = ( 𝑋 + ( 𝑌 + ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ) ) )
15 eqid ( 0g𝐺 ) = ( 0g𝐺 )
16 1 2 15 3 grprinv ( ( 𝐺 ∈ Grp ∧ 𝑌𝐵 ) → ( 𝑌 + ( 𝑁𝑌 ) ) = ( 0g𝐺 ) )
17 16 3adant2 ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( 𝑌 + ( 𝑁𝑌 ) ) = ( 0g𝐺 ) )
18 17 oveq1d ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( ( 𝑌 + ( 𝑁𝑌 ) ) + ( 𝑁𝑋 ) ) = ( ( 0g𝐺 ) + ( 𝑁𝑋 ) ) )
19 1 2 grpass ( ( 𝐺 ∈ Grp ∧ ( 𝑌𝐵 ∧ ( 𝑁𝑌 ) ∈ 𝐵 ∧ ( 𝑁𝑋 ) ∈ 𝐵 ) ) → ( ( 𝑌 + ( 𝑁𝑌 ) ) + ( 𝑁𝑋 ) ) = ( 𝑌 + ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ) )
20 4 6 8 10 19 syl13anc ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( ( 𝑌 + ( 𝑁𝑌 ) ) + ( 𝑁𝑋 ) ) = ( 𝑌 + ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ) )
21 1 2 15 grplid ( ( 𝐺 ∈ Grp ∧ ( 𝑁𝑋 ) ∈ 𝐵 ) → ( ( 0g𝐺 ) + ( 𝑁𝑋 ) ) = ( 𝑁𝑋 ) )
22 4 10 21 syl2anc ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( ( 0g𝐺 ) + ( 𝑁𝑋 ) ) = ( 𝑁𝑋 ) )
23 18 20 22 3eqtr3d ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( 𝑌 + ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ) = ( 𝑁𝑋 ) )
24 23 oveq2d ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( 𝑋 + ( 𝑌 + ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ) ) = ( 𝑋 + ( 𝑁𝑋 ) ) )
25 1 2 15 3 grprinv ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵 ) → ( 𝑋 + ( 𝑁𝑋 ) ) = ( 0g𝐺 ) )
26 25 3adant3 ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( 𝑋 + ( 𝑁𝑋 ) ) = ( 0g𝐺 ) )
27 14 24 26 3eqtrd ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( ( 𝑋 + 𝑌 ) + ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ) = ( 0g𝐺 ) )
28 1 2 grpcl ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( 𝑋 + 𝑌 ) ∈ 𝐵 )
29 1 2 15 3 grpinvid1 ( ( 𝐺 ∈ Grp ∧ ( 𝑋 + 𝑌 ) ∈ 𝐵 ∧ ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ∈ 𝐵 ) → ( ( 𝑁 ‘ ( 𝑋 + 𝑌 ) ) = ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ↔ ( ( 𝑋 + 𝑌 ) + ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ) = ( 0g𝐺 ) ) )
30 4 28 12 29 syl3anc ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( ( 𝑁 ‘ ( 𝑋 + 𝑌 ) ) = ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ↔ ( ( 𝑋 + 𝑌 ) + ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) ) = ( 0g𝐺 ) ) )
31 27 30 mpbird ( ( 𝐺 ∈ Grp ∧ 𝑋𝐵𝑌𝐵 ) → ( 𝑁 ‘ ( 𝑋 + 𝑌 ) ) = ( ( 𝑁𝑌 ) + ( 𝑁𝑋 ) ) )