Step | Hyp | Ref
| Expression |
1 | | tngngp.t |
. . . . 5
⊢ 𝑇 = (𝐺 toNrmGrp 𝑁) |
2 | | tngngp.x |
. . . . 5
⊢ 𝑋 = (Base‘𝐺) |
3 | | eqid 2739 |
. . . . 5
⊢
(dist‘𝑇) =
(dist‘𝑇) |
4 | 1, 2, 3 | tngngp2 23825 |
. . . 4
⊢ (𝑁:𝑋⟶ℝ → (𝑇 ∈ NrmGrp ↔ (𝐺 ∈ Grp ∧ (dist‘𝑇) ∈ (Met‘𝑋)))) |
5 | 4 | simprbda 499 |
. . 3
⊢ ((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) → 𝐺 ∈ Grp) |
6 | | simplr 766 |
. . . . . . 7
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → 𝑇 ∈ NrmGrp) |
7 | | simpr 485 |
. . . . . . . 8
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → 𝑥 ∈ 𝑋) |
8 | 2 | fvexi 6797 |
. . . . . . . . . . 11
⊢ 𝑋 ∈ V |
9 | | reex 10971 |
. . . . . . . . . . 11
⊢ ℝ
∈ V |
10 | | fex2 7789 |
. . . . . . . . . . 11
⊢ ((𝑁:𝑋⟶ℝ ∧ 𝑋 ∈ V ∧ ℝ ∈ V) →
𝑁 ∈
V) |
11 | 8, 9, 10 | mp3an23 1452 |
. . . . . . . . . 10
⊢ (𝑁:𝑋⟶ℝ → 𝑁 ∈ V) |
12 | 11 | ad2antrr 723 |
. . . . . . . . 9
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → 𝑁 ∈ V) |
13 | 1, 2 | tngbas 23807 |
. . . . . . . . 9
⊢ (𝑁 ∈ V → 𝑋 = (Base‘𝑇)) |
14 | 12, 13 | syl 17 |
. . . . . . . 8
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → 𝑋 = (Base‘𝑇)) |
15 | 7, 14 | eleqtrd 2842 |
. . . . . . 7
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → 𝑥 ∈ (Base‘𝑇)) |
16 | | eqid 2739 |
. . . . . . . 8
⊢
(Base‘𝑇) =
(Base‘𝑇) |
17 | | eqid 2739 |
. . . . . . . 8
⊢
(norm‘𝑇) =
(norm‘𝑇) |
18 | | eqid 2739 |
. . . . . . . 8
⊢
(0g‘𝑇) = (0g‘𝑇) |
19 | 16, 17, 18 | nmeq0 23783 |
. . . . . . 7
⊢ ((𝑇 ∈ NrmGrp ∧ 𝑥 ∈ (Base‘𝑇)) → (((norm‘𝑇)‘𝑥) = 0 ↔ 𝑥 = (0g‘𝑇))) |
20 | 6, 15, 19 | syl2anc 584 |
. . . . . 6
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → (((norm‘𝑇)‘𝑥) = 0 ↔ 𝑥 = (0g‘𝑇))) |
21 | 5 | adantr 481 |
. . . . . . . . 9
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → 𝐺 ∈ Grp) |
22 | | simpll 764 |
. . . . . . . . 9
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → 𝑁:𝑋⟶ℝ) |
23 | 1, 2, 9 | tngnm 23824 |
. . . . . . . . 9
⊢ ((𝐺 ∈ Grp ∧ 𝑁:𝑋⟶ℝ) → 𝑁 = (norm‘𝑇)) |
24 | 21, 22, 23 | syl2anc 584 |
. . . . . . . 8
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → 𝑁 = (norm‘𝑇)) |
25 | 24 | fveq1d 6785 |
. . . . . . 7
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → (𝑁‘𝑥) = ((norm‘𝑇)‘𝑥)) |
26 | 25 | eqeq1d 2741 |
. . . . . 6
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → ((𝑁‘𝑥) = 0 ↔ ((norm‘𝑇)‘𝑥) = 0)) |
27 | | tngngp.z |
. . . . . . . . 9
⊢ 0 =
(0g‘𝐺) |
28 | 1, 27 | tng0 23811 |
. . . . . . . 8
⊢ (𝑁 ∈ V → 0 =
(0g‘𝑇)) |
29 | 12, 28 | syl 17 |
. . . . . . 7
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → 0 =
(0g‘𝑇)) |
30 | 29 | eqeq2d 2750 |
. . . . . 6
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → (𝑥 = 0 ↔ 𝑥 = (0g‘𝑇))) |
31 | 20, 26, 30 | 3bitr4d 311 |
. . . . 5
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → ((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 )) |
32 | | simpllr 773 |
. . . . . . . 8
⊢ ((((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) ∧ 𝑦 ∈ 𝑋) → 𝑇 ∈ NrmGrp) |
33 | 15 | adantr 481 |
. . . . . . . 8
⊢ ((((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) ∧ 𝑦 ∈ 𝑋) → 𝑥 ∈ (Base‘𝑇)) |
34 | 14 | eleq2d 2825 |
. . . . . . . . 9
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → (𝑦 ∈ 𝑋 ↔ 𝑦 ∈ (Base‘𝑇))) |
35 | 34 | biimpa 477 |
. . . . . . . 8
⊢ ((((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) ∧ 𝑦 ∈ 𝑋) → 𝑦 ∈ (Base‘𝑇)) |
36 | | eqid 2739 |
. . . . . . . . 9
⊢
(-g‘𝑇) = (-g‘𝑇) |
37 | 16, 17, 36 | nmmtri 23787 |
. . . . . . . 8
⊢ ((𝑇 ∈ NrmGrp ∧ 𝑥 ∈ (Base‘𝑇) ∧ 𝑦 ∈ (Base‘𝑇)) → ((norm‘𝑇)‘(𝑥(-g‘𝑇)𝑦)) ≤ (((norm‘𝑇)‘𝑥) + ((norm‘𝑇)‘𝑦))) |
38 | 32, 33, 35, 37 | syl3anc 1370 |
. . . . . . 7
⊢ ((((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) ∧ 𝑦 ∈ 𝑋) → ((norm‘𝑇)‘(𝑥(-g‘𝑇)𝑦)) ≤ (((norm‘𝑇)‘𝑥) + ((norm‘𝑇)‘𝑦))) |
39 | | tngngp.m |
. . . . . . . . . . 11
⊢ − =
(-g‘𝐺) |
40 | 2, 14 | eqtr3id 2793 |
. . . . . . . . . . . 12
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → (Base‘𝐺) = (Base‘𝑇)) |
41 | | eqid 2739 |
. . . . . . . . . . . . . 14
⊢
(+g‘𝐺) = (+g‘𝐺) |
42 | 1, 41 | tngplusg 23809 |
. . . . . . . . . . . . 13
⊢ (𝑁 ∈ V →
(+g‘𝐺) =
(+g‘𝑇)) |
43 | 12, 42 | syl 17 |
. . . . . . . . . . . 12
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → (+g‘𝐺) = (+g‘𝑇)) |
44 | 40, 43 | grpsubpropd 18689 |
. . . . . . . . . . 11
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → (-g‘𝐺) = (-g‘𝑇)) |
45 | 39, 44 | eqtrid 2791 |
. . . . . . . . . 10
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → − =
(-g‘𝑇)) |
46 | 45 | oveqd 7301 |
. . . . . . . . 9
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → (𝑥 − 𝑦) = (𝑥(-g‘𝑇)𝑦)) |
47 | 24, 46 | fveq12d 6790 |
. . . . . . . 8
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → (𝑁‘(𝑥 − 𝑦)) = ((norm‘𝑇)‘(𝑥(-g‘𝑇)𝑦))) |
48 | 47 | adantr 481 |
. . . . . . 7
⊢ ((((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) ∧ 𝑦 ∈ 𝑋) → (𝑁‘(𝑥 − 𝑦)) = ((norm‘𝑇)‘(𝑥(-g‘𝑇)𝑦))) |
49 | 24 | fveq1d 6785 |
. . . . . . . . 9
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → (𝑁‘𝑦) = ((norm‘𝑇)‘𝑦)) |
50 | 25, 49 | oveq12d 7302 |
. . . . . . . 8
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → ((𝑁‘𝑥) + (𝑁‘𝑦)) = (((norm‘𝑇)‘𝑥) + ((norm‘𝑇)‘𝑦))) |
51 | 50 | adantr 481 |
. . . . . . 7
⊢ ((((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) ∧ 𝑦 ∈ 𝑋) → ((𝑁‘𝑥) + (𝑁‘𝑦)) = (((norm‘𝑇)‘𝑥) + ((norm‘𝑇)‘𝑦))) |
52 | 38, 48, 51 | 3brtr4d 5107 |
. . . . . 6
⊢ ((((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) ∧ 𝑦 ∈ 𝑋) → (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))) |
53 | 52 | ralrimiva 3104 |
. . . . 5
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))) |
54 | 31, 53 | jca 512 |
. . . 4
⊢ (((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) ∧ 𝑥 ∈ 𝑋) → (((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦)))) |
55 | 54 | ralrimiva 3104 |
. . 3
⊢ ((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) → ∀𝑥 ∈ 𝑋 (((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦)))) |
56 | 5, 55 | jca 512 |
. 2
⊢ ((𝑁:𝑋⟶ℝ ∧ 𝑇 ∈ NrmGrp) → (𝐺 ∈ Grp ∧ ∀𝑥 ∈ 𝑋 (((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))))) |
57 | | simprl 768 |
. . 3
⊢ ((𝑁:𝑋⟶ℝ ∧ (𝐺 ∈ Grp ∧ ∀𝑥 ∈ 𝑋 (((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))))) → 𝐺 ∈ Grp) |
58 | | simpl 483 |
. . 3
⊢ ((𝑁:𝑋⟶ℝ ∧ (𝐺 ∈ Grp ∧ ∀𝑥 ∈ 𝑋 (((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))))) → 𝑁:𝑋⟶ℝ) |
59 | | simpl 483 |
. . . . . 6
⊢ ((((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))) → ((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 )) |
60 | 59 | ralimi 3088 |
. . . . 5
⊢
(∀𝑥 ∈
𝑋 (((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))) → ∀𝑥 ∈ 𝑋 ((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 )) |
61 | 60 | ad2antll 726 |
. . . 4
⊢ ((𝑁:𝑋⟶ℝ ∧ (𝐺 ∈ Grp ∧ ∀𝑥 ∈ 𝑋 (((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))))) → ∀𝑥 ∈ 𝑋 ((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 )) |
62 | | fveq2 6783 |
. . . . . . 7
⊢ (𝑥 = 𝑎 → (𝑁‘𝑥) = (𝑁‘𝑎)) |
63 | 62 | eqeq1d 2741 |
. . . . . 6
⊢ (𝑥 = 𝑎 → ((𝑁‘𝑥) = 0 ↔ (𝑁‘𝑎) = 0)) |
64 | | eqeq1 2743 |
. . . . . 6
⊢ (𝑥 = 𝑎 → (𝑥 = 0 ↔ 𝑎 = 0 )) |
65 | 63, 64 | bibi12d 346 |
. . . . 5
⊢ (𝑥 = 𝑎 → (((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ↔ ((𝑁‘𝑎) = 0 ↔ 𝑎 = 0 ))) |
66 | 65 | rspccva 3561 |
. . . 4
⊢
((∀𝑥 ∈
𝑋 ((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ 𝑎 ∈ 𝑋) → ((𝑁‘𝑎) = 0 ↔ 𝑎 = 0 )) |
67 | 61, 66 | sylan 580 |
. . 3
⊢ (((𝑁:𝑋⟶ℝ ∧ (𝐺 ∈ Grp ∧ ∀𝑥 ∈ 𝑋 (((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))))) ∧ 𝑎 ∈ 𝑋) → ((𝑁‘𝑎) = 0 ↔ 𝑎 = 0 )) |
68 | | simpr 485 |
. . . . . 6
⊢ ((((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))) → ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))) |
69 | 68 | ralimi 3088 |
. . . . 5
⊢
(∀𝑥 ∈
𝑋 (((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))) → ∀𝑥 ∈ 𝑋 ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))) |
70 | 69 | ad2antll 726 |
. . . 4
⊢ ((𝑁:𝑋⟶ℝ ∧ (𝐺 ∈ Grp ∧ ∀𝑥 ∈ 𝑋 (((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))))) → ∀𝑥 ∈ 𝑋 ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))) |
71 | | fvoveq1 7307 |
. . . . . . 7
⊢ (𝑥 = 𝑎 → (𝑁‘(𝑥 − 𝑦)) = (𝑁‘(𝑎 − 𝑦))) |
72 | 62 | oveq1d 7299 |
. . . . . . 7
⊢ (𝑥 = 𝑎 → ((𝑁‘𝑥) + (𝑁‘𝑦)) = ((𝑁‘𝑎) + (𝑁‘𝑦))) |
73 | 71, 72 | breq12d 5088 |
. . . . . 6
⊢ (𝑥 = 𝑎 → ((𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦)) ↔ (𝑁‘(𝑎 − 𝑦)) ≤ ((𝑁‘𝑎) + (𝑁‘𝑦)))) |
74 | | oveq2 7292 |
. . . . . . . 8
⊢ (𝑦 = 𝑏 → (𝑎 − 𝑦) = (𝑎 − 𝑏)) |
75 | 74 | fveq2d 6787 |
. . . . . . 7
⊢ (𝑦 = 𝑏 → (𝑁‘(𝑎 − 𝑦)) = (𝑁‘(𝑎 − 𝑏))) |
76 | | fveq2 6783 |
. . . . . . . 8
⊢ (𝑦 = 𝑏 → (𝑁‘𝑦) = (𝑁‘𝑏)) |
77 | 76 | oveq2d 7300 |
. . . . . . 7
⊢ (𝑦 = 𝑏 → ((𝑁‘𝑎) + (𝑁‘𝑦)) = ((𝑁‘𝑎) + (𝑁‘𝑏))) |
78 | 75, 77 | breq12d 5088 |
. . . . . 6
⊢ (𝑦 = 𝑏 → ((𝑁‘(𝑎 − 𝑦)) ≤ ((𝑁‘𝑎) + (𝑁‘𝑦)) ↔ (𝑁‘(𝑎 − 𝑏)) ≤ ((𝑁‘𝑎) + (𝑁‘𝑏)))) |
79 | 73, 78 | rspc2va 3572 |
. . . . 5
⊢ (((𝑎 ∈ 𝑋 ∧ 𝑏 ∈ 𝑋) ∧ ∀𝑥 ∈ 𝑋 ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))) → (𝑁‘(𝑎 − 𝑏)) ≤ ((𝑁‘𝑎) + (𝑁‘𝑏))) |
80 | 79 | ancoms 459 |
. . . 4
⊢
((∀𝑥 ∈
𝑋 ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦)) ∧ (𝑎 ∈ 𝑋 ∧ 𝑏 ∈ 𝑋)) → (𝑁‘(𝑎 − 𝑏)) ≤ ((𝑁‘𝑎) + (𝑁‘𝑏))) |
81 | 70, 80 | sylan 580 |
. . 3
⊢ (((𝑁:𝑋⟶ℝ ∧ (𝐺 ∈ Grp ∧ ∀𝑥 ∈ 𝑋 (((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))))) ∧ (𝑎 ∈ 𝑋 ∧ 𝑏 ∈ 𝑋)) → (𝑁‘(𝑎 − 𝑏)) ≤ ((𝑁‘𝑎) + (𝑁‘𝑏))) |
82 | 1, 2, 39, 27, 57, 58, 67, 81 | tngngpd 23826 |
. 2
⊢ ((𝑁:𝑋⟶ℝ ∧ (𝐺 ∈ Grp ∧ ∀𝑥 ∈ 𝑋 (((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦))))) → 𝑇 ∈ NrmGrp) |
83 | 56, 82 | impbida 798 |
1
⊢ (𝑁:𝑋⟶ℝ → (𝑇 ∈ NrmGrp ↔ (𝐺 ∈ Grp ∧ ∀𝑥 ∈ 𝑋 (((𝑁‘𝑥) = 0 ↔ 𝑥 = 0 ) ∧ ∀𝑦 ∈ 𝑋 (𝑁‘(𝑥 − 𝑦)) ≤ ((𝑁‘𝑥) + (𝑁‘𝑦)))))) |