Theorem grpid 18963

Description: Two ways of saying that an element of a group is the identity element. Provides a convenient way to compute the value of the identity element. (Contributed by NM, 24-Aug-2011.)

Hypotheses

Ref	Expression
grpinveu.b	⊢ 𝐵 = (Base‘𝐺)
grpinveu.p	⊢ + = (+g‘𝐺)
grpinveu.o	⊢ 0 = (0g‘𝐺)

Assertion

Ref	Expression
grpid	⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵) → ((𝑋 + 𝑋) = 𝑋 ↔ 0 = 𝑋))

Proof of Theorem grpid

Step	Hyp	Ref	Expression
1		eqcom 2743	. 2 ⊢ ( 0 = 𝑋 ↔ 𝑋 = 0 )
2		grpinveu.b	. . . . . . 7 ⊢ 𝐵 = (Base‘𝐺)
3		grpinveu.o	. . . . . . 7 ⊢ 0 = (0g‘𝐺)
4	2, 3	grpidcl 18953	. . . . . 6 ⊢ (𝐺 ∈ Grp → 0 ∈ 𝐵)
5		grpinveu.p	. . . . . . . 8 ⊢ + = (+g‘𝐺)
6	2, 5	grprcan 18961	. . . . . . 7 ⊢ ((𝐺 ∈ Grp ∧ (𝑋 ∈ 𝐵 ∧ 0 ∈ 𝐵 ∧ 𝑋 ∈ 𝐵)) → ((𝑋 + 𝑋) = ( 0 + 𝑋) ↔ 𝑋 = 0 ))
7	6	3exp2 1355	. . . . . 6 ⊢ (𝐺 ∈ Grp → (𝑋 ∈ 𝐵 → ( 0 ∈ 𝐵 → (𝑋 ∈ 𝐵 → ((𝑋 + 𝑋) = ( 0 + 𝑋) ↔ 𝑋 = 0 )))))
8	4, 7	mpid 44	. . . . 5 ⊢ (𝐺 ∈ Grp → (𝑋 ∈ 𝐵 → (𝑋 ∈ 𝐵 → ((𝑋 + 𝑋) = ( 0 + 𝑋) ↔ 𝑋 = 0 ))))
9	8	pm2.43d 53	. . . 4 ⊢ (𝐺 ∈ Grp → (𝑋 ∈ 𝐵 → ((𝑋 + 𝑋) = ( 0 + 𝑋) ↔ 𝑋 = 0 )))
10	9	imp 406	. . 3 ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵) → ((𝑋 + 𝑋) = ( 0 + 𝑋) ↔ 𝑋 = 0 ))
11	2, 5, 3	grplid 18955	. . . 4 ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵) → ( 0 + 𝑋) = 𝑋)
12	11	eqeq2d 2747	. . 3 ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵) → ((𝑋 + 𝑋) = ( 0 + 𝑋) ↔ (𝑋 + 𝑋) = 𝑋))
13	10, 12	bitr3d 281	. 2 ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵) → (𝑋 = 0 ↔ (𝑋 + 𝑋) = 𝑋))
14	1, 13	bitr2id 284	1 ⊢ ((𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵) → ((𝑋 + 𝑋) = 𝑋 ↔ 0 = 𝑋))

Syntax hints:   → wi 4   ↔ wb 206   ∧ wa 395   = wceq 1540   ∈ wcel 2109  ‘cfv 6536  (class class class)co 7410  Basecbs 17233  +_gcplusg 17276  0_gc0g 17458  Grpcgrp 18921

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1795  ax-4 1809  ax-5 1910  ax-6 1967  ax-7 2008  ax-8 2111  ax-9 2119  ax-10 2142  ax-11 2158  ax-12 2178  ax-ext 2708  ax-sep 5271  ax-nul 5281  ax-pr 5407

This theorem depends on definitions:  df-bi 207  df-an 396  df-or 848  df-3an 1088  df-tru 1543  df-fal 1553  df-ex 1780  df-nf 1784  df-sb 2066  df-mo 2540  df-eu 2569  df-clab 2715  df-cleq 2728  df-clel 2810  df-nfc 2886  df-ne 2934  df-ral 3053  df-rex 3062  df-rmo 3364  df-reu 3365  df-rab 3421  df-v 3466  df-sbc 3771  df-dif 3934  df-un 3936  df-ss 3948  df-nul 4314  df-if 4506  df-sn 4607  df-pr 4609  df-op 4613  df-uni 4889  df-br 5125  df-opab 5187  df-mpt 5207  df-id 5553  df-xp 5665  df-rel 5666  df-cnv 5667  df-co 5668  df-dm 5669  df-iota 6489  df-fun 6538  df-fv 6544  df-riota 7367  df-ov 7413  df-0g 17460  df-mgm 18623  df-sgrp 18702  df-mnd 18718  df-grp 18924

This theorem is referenced by:  isgrpid2  18964  grpidd2  18965  subg0  19120  qus0  19177  ghmid  19210  isdrng2  20708  lmod0vid  20856  cnfld0  21360  psr0  21923  psd1  22110  ldual0v  39173  erng0g  41018