Theorem gexval 19610

Description: Value of the exponent of a group. (Contributed by Mario Carneiro, 23-Apr-2016.) (Revised by AV, 26-Sep-2020.)

Hypotheses

Ref	Expression
gexval.1	⊢ 𝑋 = (Base‘𝐺)
gexval.2	⊢ · = (.g‘𝐺)
gexval.3	⊢ 0 = (0g‘𝐺)
gexval.4	⊢ 𝐸 = (gEx‘𝐺)
gexval.i	⊢ 𝐼 = {𝑦 ∈ ℕ ∣ ∀𝑥 ∈ 𝑋 (𝑦 · 𝑥) = 0 }

Assertion

Ref	Expression
gexval	⊢ (𝐺 ∈ 𝑉 → 𝐸 = if(𝐼 = ∅, 0, inf(𝐼, ℝ, < )))

Distinct variable groups:   𝑥,𝑦, 0   𝑥,𝐺,𝑦   𝑥,𝑉,𝑦   𝑥, · ,𝑦   𝑥,𝑋

Allowed substitution hints:   𝐸(𝑥,𝑦)   𝐼(𝑥,𝑦)   𝑋(𝑦)

Proof of Theorem gexval

Dummy variables 𝑔 𝑖 are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		gexval.4	. 2 ⊢ 𝐸 = (gEx‘𝐺)
2		df-gex 19561	. . 3 ⊢ gEx = (𝑔 ∈ V ↦ ⦋{𝑦 ∈ ℕ ∣ ∀𝑥 ∈ (Base‘𝑔)(𝑦(.g‘𝑔)𝑥) = (0g‘𝑔)} / 𝑖⦌if(𝑖 = ∅, 0, inf(𝑖, ℝ, < )))
3		nnex 12269	. . . . . 6 ⊢ ℕ ∈ V
4	3	rabex 5344	. . . . 5 ⊢ {𝑦 ∈ ℕ ∣ ∀𝑥 ∈ (Base‘𝑔)(𝑦(.g‘𝑔)𝑥) = (0g‘𝑔)} ∈ V
5	4	a1i 11	. . . 4 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → {𝑦 ∈ ℕ ∣ ∀𝑥 ∈ (Base‘𝑔)(𝑦(.g‘𝑔)𝑥) = (0g‘𝑔)} ∈ V)
6		simpr 484	. . . . . . . . . . . . 13 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → 𝑔 = 𝐺)
7	6	fveq2d 6910	. . . . . . . . . . . 12 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → (Base‘𝑔) = (Base‘𝐺))
8		gexval.1	. . . . . . . . . . . 12 ⊢ 𝑋 = (Base‘𝐺)
9	7, 8	eqtr4di 2792	. . . . . . . . . . 11 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → (Base‘𝑔) = 𝑋)
10	6	fveq2d 6910	. . . . . . . . . . . . . 14 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → (.g‘𝑔) = (.g‘𝐺))
11		gexval.2	. . . . . . . . . . . . . 14 ⊢ · = (.g‘𝐺)
12	10, 11	eqtr4di 2792	. . . . . . . . . . . . 13 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → (.g‘𝑔) = · )
13	12	oveqd 7447	. . . . . . . . . . . 12 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → (𝑦(.g‘𝑔)𝑥) = (𝑦 · 𝑥))
14	6	fveq2d 6910	. . . . . . . . . . . . 13 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → (0g‘𝑔) = (0g‘𝐺))
15		gexval.3	. . . . . . . . . . . . 13 ⊢ 0 = (0g‘𝐺)
16	14, 15	eqtr4di 2792	. . . . . . . . . . . 12 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → (0g‘𝑔) = 0 )
17	13, 16	eqeq12d 2750	. . . . . . . . . . 11 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → ((𝑦(.g‘𝑔)𝑥) = (0g‘𝑔) ↔ (𝑦 · 𝑥) = 0 ))
18	9, 17	raleqbidv 3343	. . . . . . . . . 10 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → (∀𝑥 ∈ (Base‘𝑔)(𝑦(.g‘𝑔)𝑥) = (0g‘𝑔) ↔ ∀𝑥 ∈ 𝑋 (𝑦 · 𝑥) = 0 ))
19	18	rabbidv 3440	. . . . . . . . 9 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → {𝑦 ∈ ℕ ∣ ∀𝑥 ∈ (Base‘𝑔)(𝑦(.g‘𝑔)𝑥) = (0g‘𝑔)} = {𝑦 ∈ ℕ ∣ ∀𝑥 ∈ 𝑋 (𝑦 · 𝑥) = 0 })
20		gexval.i	. . . . . . . . 9 ⊢ 𝐼 = {𝑦 ∈ ℕ ∣ ∀𝑥 ∈ 𝑋 (𝑦 · 𝑥) = 0 }
21	19, 20	eqtr4di 2792	. . . . . . . 8 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → {𝑦 ∈ ℕ ∣ ∀𝑥 ∈ (Base‘𝑔)(𝑦(.g‘𝑔)𝑥) = (0g‘𝑔)} = 𝐼)
22	21	eqeq2d 2745	. . . . . . 7 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → (𝑖 = {𝑦 ∈ ℕ ∣ ∀𝑥 ∈ (Base‘𝑔)(𝑦(.g‘𝑔)𝑥) = (0g‘𝑔)} ↔ 𝑖 = 𝐼))
23	22	biimpa 476	. . . . . 6 ⊢ (((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) ∧ 𝑖 = {𝑦 ∈ ℕ ∣ ∀𝑥 ∈ (Base‘𝑔)(𝑦(.g‘𝑔)𝑥) = (0g‘𝑔)}) → 𝑖 = 𝐼)
24	23	eqeq1d 2736	. . . . 5 ⊢ (((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) ∧ 𝑖 = {𝑦 ∈ ℕ ∣ ∀𝑥 ∈ (Base‘𝑔)(𝑦(.g‘𝑔)𝑥) = (0g‘𝑔)}) → (𝑖 = ∅ ↔ 𝐼 = ∅))
25	23	infeq1d 9514	. . . . 5 ⊢ (((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) ∧ 𝑖 = {𝑦 ∈ ℕ ∣ ∀𝑥 ∈ (Base‘𝑔)(𝑦(.g‘𝑔)𝑥) = (0g‘𝑔)}) → inf(𝑖, ℝ, < ) = inf(𝐼, ℝ, < ))
26	24, 25	ifbieq2d 4556	. . . 4 ⊢ (((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) ∧ 𝑖 = {𝑦 ∈ ℕ ∣ ∀𝑥 ∈ (Base‘𝑔)(𝑦(.g‘𝑔)𝑥) = (0g‘𝑔)}) → if(𝑖 = ∅, 0, inf(𝑖, ℝ, < )) = if(𝐼 = ∅, 0, inf(𝐼, ℝ, < )))
27	5, 26	csbied 3945	. . 3 ⊢ ((𝐺 ∈ 𝑉 ∧ 𝑔 = 𝐺) → ⦋{𝑦 ∈ ℕ ∣ ∀𝑥 ∈ (Base‘𝑔)(𝑦(.g‘𝑔)𝑥) = (0g‘𝑔)} / 𝑖⦌if(𝑖 = ∅, 0, inf(𝑖, ℝ, < )) = if(𝐼 = ∅, 0, inf(𝐼, ℝ, < )))
28		elex 3498	. . 3 ⊢ (𝐺 ∈ 𝑉 → 𝐺 ∈ V)
29		c0ex 11252	. . . . 5 ⊢ 0 ∈ V
30		ltso 11338	. . . . . 6 ⊢ < Or ℝ
31	30	infex 9530	. . . . 5 ⊢ inf(𝐼, ℝ, < ) ∈ V
32	29, 31	ifex 4580	. . . 4 ⊢ if(𝐼 = ∅, 0, inf(𝐼, ℝ, < )) ∈ V
33	32	a1i 11	. . 3 ⊢ (𝐺 ∈ 𝑉 → if(𝐼 = ∅, 0, inf(𝐼, ℝ, < )) ∈ V)
34	2, 27, 28, 33	fvmptd2 7023	. 2 ⊢ (𝐺 ∈ 𝑉 → (gEx‘𝐺) = if(𝐼 = ∅, 0, inf(𝐼, ℝ, < )))
35	1, 34	eqtrid 2786	1 ⊢ (𝐺 ∈ 𝑉 → 𝐸 = if(𝐼 = ∅, 0, inf(𝐼, ℝ, < )))

Syntax hints:   → wi 4   ∧ wa 395   = wceq 1536   ∈ wcel 2105  ∀wral 3058  {crab 3432  Vcvv 3477  ⦋csb 3907  ∅c0 4338  ifcif 4530  ‘cfv 6562  (class class class)co 7430  infcinf 9478  ℝcr 11151  0cc0 11152   < clt 11292  ℕcn 12263  Basecbs 17244  0_gc0g 17485  ._gcmg 19097  gExcgex 19557

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1791  ax-4 1805  ax-5 1907  ax-6 1964  ax-7 2004  ax-8 2107  ax-9 2115  ax-10 2138  ax-11 2154  ax-12 2174  ax-ext 2705  ax-sep 5301  ax-nul 5311  ax-pow 5370  ax-pr 5437  ax-un 7753  ax-cnex 11208  ax-resscn 11209  ax-1cn 11210  ax-icn 11211  ax-addcl 11212  ax-mulcl 11214  ax-i2m1 11220  ax-pre-lttri 11226  ax-pre-lttrn 11227

This theorem depends on definitions:  df-bi 207  df-an 396  df-or 848  df-3or 1087  df-3an 1088  df-tru 1539  df-fal 1549  df-ex 1776  df-nf 1780  df-sb 2062  df-mo 2537  df-eu 2566  df-clab 2712  df-cleq 2726  df-clel 2813  df-nfc 2889  df-ne 2938  df-nel 3044  df-ral 3059  df-rex 3068  df-rmo 3377  df-reu 3378  df-rab 3433  df-v 3479  df-sbc 3791  df-csb 3908  df-dif 3965  df-un 3967  df-in 3969  df-ss 3979  df-pss 3982  df-nul 4339  df-if 4531  df-pw 4606  df-sn 4631  df-pr 4633  df-op 4637  df-uni 4912  df-iun 4997  df-br 5148  df-opab 5210  df-mpt 5231  df-tr 5265  df-id 5582  df-eprel 5588  df-po 5596  df-so 5597  df-fr 5640  df-we 5642  df-xp 5694  df-rel 5695  df-cnv 5696  df-co 5697  df-dm 5698  df-rn 5699  df-res 5700  df-ima 5701  df-pred 6322  df-ord 6388  df-on 6389  df-lim 6390  df-suc 6391  df-iota 6515  df-fun 6564  df-fn 6565  df-f 6566  df-f1 6567  df-fo 6568  df-f1o 6569  df-fv 6570  df-ov 7433  df-om 7887  df-2nd 8013  df-frecs 8304  df-wrecs 8335  df-recs 8409  df-rdg 8448  df-er 8743  df-en 8984  df-dom 8985  df-sdom 8986  df-sup 9479  df-inf 9480  df-pnf 11294  df-mnf 11295  df-ltxr 11297  df-nn 12264  df-gex 19561

This theorem is referenced by:  gexlem1  19611  gexlem2  19614