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| Description: The identity homomorphism on a group. (Contributed by Stefan O'Rear, 31-Dec-2014.) | 
| Ref | Expression | 
|---|---|
| idghm.b | ⊢ 𝐵 = (Base‘𝐺) | 
| Ref | Expression | 
|---|---|
| idghm | ⊢ (𝐺 ∈ Grp → ( I ↾ 𝐵) ∈ (𝐺 GrpHom 𝐺)) | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | id 22 | . 2 ⊢ (𝐺 ∈ Grp → 𝐺 ∈ Grp) | |
| 2 | idghm.b | . . . . . . . 8 ⊢ 𝐵 = (Base‘𝐺) | |
| 3 | eqid 2736 | . . . . . . . 8 ⊢ (+g‘𝐺) = (+g‘𝐺) | |
| 4 | 2, 3 | grpcl 18960 | . . . . . . 7 ⊢ ((𝐺 ∈ Grp ∧ 𝑎 ∈ 𝐵 ∧ 𝑏 ∈ 𝐵) → (𝑎(+g‘𝐺)𝑏) ∈ 𝐵) | 
| 5 | 4 | 3expb 1120 | . . . . . 6 ⊢ ((𝐺 ∈ Grp ∧ (𝑎 ∈ 𝐵 ∧ 𝑏 ∈ 𝐵)) → (𝑎(+g‘𝐺)𝑏) ∈ 𝐵) | 
| 6 | fvresi 7194 | . . . . . 6 ⊢ ((𝑎(+g‘𝐺)𝑏) ∈ 𝐵 → (( I ↾ 𝐵)‘(𝑎(+g‘𝐺)𝑏)) = (𝑎(+g‘𝐺)𝑏)) | |
| 7 | 5, 6 | syl 17 | . . . . 5 ⊢ ((𝐺 ∈ Grp ∧ (𝑎 ∈ 𝐵 ∧ 𝑏 ∈ 𝐵)) → (( I ↾ 𝐵)‘(𝑎(+g‘𝐺)𝑏)) = (𝑎(+g‘𝐺)𝑏)) | 
| 8 | fvresi 7194 | . . . . . . 7 ⊢ (𝑎 ∈ 𝐵 → (( I ↾ 𝐵)‘𝑎) = 𝑎) | |
| 9 | fvresi 7194 | . . . . . . 7 ⊢ (𝑏 ∈ 𝐵 → (( I ↾ 𝐵)‘𝑏) = 𝑏) | |
| 10 | 8, 9 | oveqan12d 7451 | . . . . . 6 ⊢ ((𝑎 ∈ 𝐵 ∧ 𝑏 ∈ 𝐵) → ((( I ↾ 𝐵)‘𝑎)(+g‘𝐺)(( I ↾ 𝐵)‘𝑏)) = (𝑎(+g‘𝐺)𝑏)) | 
| 11 | 10 | adantl 481 | . . . . 5 ⊢ ((𝐺 ∈ Grp ∧ (𝑎 ∈ 𝐵 ∧ 𝑏 ∈ 𝐵)) → ((( I ↾ 𝐵)‘𝑎)(+g‘𝐺)(( I ↾ 𝐵)‘𝑏)) = (𝑎(+g‘𝐺)𝑏)) | 
| 12 | 7, 11 | eqtr4d 2779 | . . . 4 ⊢ ((𝐺 ∈ Grp ∧ (𝑎 ∈ 𝐵 ∧ 𝑏 ∈ 𝐵)) → (( I ↾ 𝐵)‘(𝑎(+g‘𝐺)𝑏)) = ((( I ↾ 𝐵)‘𝑎)(+g‘𝐺)(( I ↾ 𝐵)‘𝑏))) | 
| 13 | 12 | ralrimivva 3201 | . . 3 ⊢ (𝐺 ∈ Grp → ∀𝑎 ∈ 𝐵 ∀𝑏 ∈ 𝐵 (( I ↾ 𝐵)‘(𝑎(+g‘𝐺)𝑏)) = ((( I ↾ 𝐵)‘𝑎)(+g‘𝐺)(( I ↾ 𝐵)‘𝑏))) | 
| 14 | f1oi 6885 | . . . 4 ⊢ ( I ↾ 𝐵):𝐵–1-1-onto→𝐵 | |
| 15 | f1of 6847 | . . . 4 ⊢ (( I ↾ 𝐵):𝐵–1-1-onto→𝐵 → ( I ↾ 𝐵):𝐵⟶𝐵) | |
| 16 | 14, 15 | ax-mp 5 | . . 3 ⊢ ( I ↾ 𝐵):𝐵⟶𝐵 | 
| 17 | 13, 16 | jctil 519 | . 2 ⊢ (𝐺 ∈ Grp → (( I ↾ 𝐵):𝐵⟶𝐵 ∧ ∀𝑎 ∈ 𝐵 ∀𝑏 ∈ 𝐵 (( I ↾ 𝐵)‘(𝑎(+g‘𝐺)𝑏)) = ((( I ↾ 𝐵)‘𝑎)(+g‘𝐺)(( I ↾ 𝐵)‘𝑏)))) | 
| 18 | 2, 2, 3, 3 | isghm 19234 | . 2 ⊢ (( I ↾ 𝐵) ∈ (𝐺 GrpHom 𝐺) ↔ ((𝐺 ∈ Grp ∧ 𝐺 ∈ Grp) ∧ (( I ↾ 𝐵):𝐵⟶𝐵 ∧ ∀𝑎 ∈ 𝐵 ∀𝑏 ∈ 𝐵 (( I ↾ 𝐵)‘(𝑎(+g‘𝐺)𝑏)) = ((( I ↾ 𝐵)‘𝑎)(+g‘𝐺)(( I ↾ 𝐵)‘𝑏))))) | 
| 19 | 1, 1, 17, 18 | syl21anbrc 1344 | 1 ⊢ (𝐺 ∈ Grp → ( I ↾ 𝐵) ∈ (𝐺 GrpHom 𝐺)) | 
| Colors of variables: wff setvar class | 
| Syntax hints: → wi 4 ∧ wa 395 = wceq 1539 ∈ wcel 2107 ∀wral 3060 I cid 5576 ↾ cres 5686 ⟶wf 6556 –1-1-onto→wf1o 6559 ‘cfv 6560 (class class class)co 7432 Basecbs 17248 +gcplusg 17298 Grpcgrp 18952 GrpHom cghm 19231 | 
| This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1794 ax-4 1808 ax-5 1909 ax-6 1966 ax-7 2006 ax-8 2109 ax-9 2117 ax-10 2140 ax-11 2156 ax-12 2176 ax-ext 2707 ax-sep 5295 ax-nul 5305 ax-pow 5364 ax-pr 5431 ax-un 7756 | 
| This theorem depends on definitions: df-bi 207 df-an 396 df-or 848 df-3an 1088 df-tru 1542 df-fal 1552 df-ex 1779 df-nf 1783 df-sb 2064 df-mo 2539 df-eu 2568 df-clab 2714 df-cleq 2728 df-clel 2815 df-nfc 2891 df-ne 2940 df-ral 3061 df-rex 3070 df-rab 3436 df-v 3481 df-sbc 3788 df-csb 3899 df-dif 3953 df-un 3955 df-in 3957 df-ss 3967 df-nul 4333 df-if 4525 df-pw 4601 df-sn 4626 df-pr 4628 df-op 4632 df-uni 4907 df-iun 4992 df-br 5143 df-opab 5205 df-mpt 5225 df-id 5577 df-xp 5690 df-rel 5691 df-cnv 5692 df-co 5693 df-dm 5694 df-rn 5695 df-res 5696 df-ima 5697 df-iota 6513 df-fun 6562 df-fn 6563 df-f 6564 df-f1 6565 df-fo 6566 df-f1o 6567 df-fv 6568 df-ov 7435 df-oprab 7436 df-mpo 7437 df-1st 8015 df-2nd 8016 df-map 8869 df-mgm 18654 df-sgrp 18733 df-mnd 18749 df-grp 18955 df-ghm 19232 | 
| This theorem is referenced by: gicref 19291 symgga 19426 0frgp 19798 idrnghm 20459 idrhm 20491 idlmhm 21041 frgpcyg 21593 nmoid 24764 idnghm 24765 | 
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