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| Description: If the metric 𝐷 is "strongly finer" than 𝐶 (meaning that there is a positive real constant 𝑅 such that 𝐶(𝑥, 𝑦) ≤ 𝑅 · 𝐷(𝑥, 𝑦)), then 𝐷 generates a finer topology. (Using this theorem twice in each direction states that if two metrics are strongly equivalent, then they generate the same topology.) (Contributed by Mario Carneiro, 14-Sep-2015.) | 
| Ref | Expression | 
|---|---|
| metequiv.3 | ⊢ 𝐽 = (MetOpen‘𝐶) | 
| metequiv.4 | ⊢ 𝐾 = (MetOpen‘𝐷) | 
| metss2.1 | ⊢ (𝜑 → 𝐶 ∈ (Met‘𝑋)) | 
| metss2.2 | ⊢ (𝜑 → 𝐷 ∈ (Met‘𝑋)) | 
| metss2.3 | ⊢ (𝜑 → 𝑅 ∈ ℝ+) | 
| metss2.4 | ⊢ ((𝜑 ∧ (𝑥 ∈ 𝑋 ∧ 𝑦 ∈ 𝑋)) → (𝑥𝐶𝑦) ≤ (𝑅 · (𝑥𝐷𝑦))) | 
| Ref | Expression | 
|---|---|
| metss2 | ⊢ (𝜑 → 𝐽 ⊆ 𝐾) | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | simpr 484 | . . . . 5 ⊢ ((𝑥 ∈ 𝑋 ∧ 𝑟 ∈ ℝ+) → 𝑟 ∈ ℝ+) | |
| 2 | metss2.3 | . . . . 5 ⊢ (𝜑 → 𝑅 ∈ ℝ+) | |
| 3 | rpdivcl 13060 | . . . . 5 ⊢ ((𝑟 ∈ ℝ+ ∧ 𝑅 ∈ ℝ+) → (𝑟 / 𝑅) ∈ ℝ+) | |
| 4 | 1, 2, 3 | syl2anr 597 | . . . 4 ⊢ ((𝜑 ∧ (𝑥 ∈ 𝑋 ∧ 𝑟 ∈ ℝ+)) → (𝑟 / 𝑅) ∈ ℝ+) | 
| 5 | metequiv.3 | . . . . 5 ⊢ 𝐽 = (MetOpen‘𝐶) | |
| 6 | metequiv.4 | . . . . 5 ⊢ 𝐾 = (MetOpen‘𝐷) | |
| 7 | metss2.1 | . . . . 5 ⊢ (𝜑 → 𝐶 ∈ (Met‘𝑋)) | |
| 8 | metss2.2 | . . . . 5 ⊢ (𝜑 → 𝐷 ∈ (Met‘𝑋)) | |
| 9 | metss2.4 | . . . . 5 ⊢ ((𝜑 ∧ (𝑥 ∈ 𝑋 ∧ 𝑦 ∈ 𝑋)) → (𝑥𝐶𝑦) ≤ (𝑅 · (𝑥𝐷𝑦))) | |
| 10 | 5, 6, 7, 8, 2, 9 | metss2lem 24524 | . . . 4 ⊢ ((𝜑 ∧ (𝑥 ∈ 𝑋 ∧ 𝑟 ∈ ℝ+)) → (𝑥(ball‘𝐷)(𝑟 / 𝑅)) ⊆ (𝑥(ball‘𝐶)𝑟)) | 
| 11 | oveq2 7439 | . . . . . 6 ⊢ (𝑠 = (𝑟 / 𝑅) → (𝑥(ball‘𝐷)𝑠) = (𝑥(ball‘𝐷)(𝑟 / 𝑅))) | |
| 12 | 11 | sseq1d 4015 | . . . . 5 ⊢ (𝑠 = (𝑟 / 𝑅) → ((𝑥(ball‘𝐷)𝑠) ⊆ (𝑥(ball‘𝐶)𝑟) ↔ (𝑥(ball‘𝐷)(𝑟 / 𝑅)) ⊆ (𝑥(ball‘𝐶)𝑟))) | 
| 13 | 12 | rspcev 3622 | . . . 4 ⊢ (((𝑟 / 𝑅) ∈ ℝ+ ∧ (𝑥(ball‘𝐷)(𝑟 / 𝑅)) ⊆ (𝑥(ball‘𝐶)𝑟)) → ∃𝑠 ∈ ℝ+ (𝑥(ball‘𝐷)𝑠) ⊆ (𝑥(ball‘𝐶)𝑟)) | 
| 14 | 4, 10, 13 | syl2anc 584 | . . 3 ⊢ ((𝜑 ∧ (𝑥 ∈ 𝑋 ∧ 𝑟 ∈ ℝ+)) → ∃𝑠 ∈ ℝ+ (𝑥(ball‘𝐷)𝑠) ⊆ (𝑥(ball‘𝐶)𝑟)) | 
| 15 | 14 | ralrimivva 3202 | . 2 ⊢ (𝜑 → ∀𝑥 ∈ 𝑋 ∀𝑟 ∈ ℝ+ ∃𝑠 ∈ ℝ+ (𝑥(ball‘𝐷)𝑠) ⊆ (𝑥(ball‘𝐶)𝑟)) | 
| 16 | metxmet 24344 | . . . 4 ⊢ (𝐶 ∈ (Met‘𝑋) → 𝐶 ∈ (∞Met‘𝑋)) | |
| 17 | 7, 16 | syl 17 | . . 3 ⊢ (𝜑 → 𝐶 ∈ (∞Met‘𝑋)) | 
| 18 | metxmet 24344 | . . . 4 ⊢ (𝐷 ∈ (Met‘𝑋) → 𝐷 ∈ (∞Met‘𝑋)) | |
| 19 | 8, 18 | syl 17 | . . 3 ⊢ (𝜑 → 𝐷 ∈ (∞Met‘𝑋)) | 
| 20 | 5, 6 | metss 24521 | . . 3 ⊢ ((𝐶 ∈ (∞Met‘𝑋) ∧ 𝐷 ∈ (∞Met‘𝑋)) → (𝐽 ⊆ 𝐾 ↔ ∀𝑥 ∈ 𝑋 ∀𝑟 ∈ ℝ+ ∃𝑠 ∈ ℝ+ (𝑥(ball‘𝐷)𝑠) ⊆ (𝑥(ball‘𝐶)𝑟))) | 
| 21 | 17, 19, 20 | syl2anc 584 | . 2 ⊢ (𝜑 → (𝐽 ⊆ 𝐾 ↔ ∀𝑥 ∈ 𝑋 ∀𝑟 ∈ ℝ+ ∃𝑠 ∈ ℝ+ (𝑥(ball‘𝐷)𝑠) ⊆ (𝑥(ball‘𝐶)𝑟))) | 
| 22 | 15, 21 | mpbird 257 | 1 ⊢ (𝜑 → 𝐽 ⊆ 𝐾) | 
| Colors of variables: wff setvar class | 
| Syntax hints: → wi 4 ↔ wb 206 ∧ wa 395 = wceq 1540 ∈ wcel 2108 ∀wral 3061 ∃wrex 3070 ⊆ wss 3951 class class class wbr 5143 ‘cfv 6561 (class class class)co 7431 · cmul 11160 ≤ cle 11296 / cdiv 11920 ℝ+crp 13034 ∞Metcxmet 21349 Metcmet 21350 ballcbl 21351 MetOpencmopn 21354 | 
| 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 2007 ax-8 2110 ax-9 2118 ax-10 2141 ax-11 2157 ax-12 2177 ax-ext 2708 ax-sep 5296 ax-nul 5306 ax-pow 5365 ax-pr 5432 ax-un 7755 ax-cnex 11211 ax-resscn 11212 ax-1cn 11213 ax-icn 11214 ax-addcl 11215 ax-addrcl 11216 ax-mulcl 11217 ax-mulrcl 11218 ax-mulcom 11219 ax-addass 11220 ax-mulass 11221 ax-distr 11222 ax-i2m1 11223 ax-1ne0 11224 ax-1rid 11225 ax-rnegex 11226 ax-rrecex 11227 ax-cnre 11228 ax-pre-lttri 11229 ax-pre-lttrn 11230 ax-pre-ltadd 11231 ax-pre-mulgt0 11232 ax-pre-sup 11233 | 
| This theorem depends on definitions: df-bi 207 df-an 396 df-or 849 df-3or 1088 df-3an 1089 df-tru 1543 df-fal 1553 df-ex 1780 df-nf 1784 df-sb 2065 df-mo 2540 df-eu 2569 df-clab 2715 df-cleq 2729 df-clel 2816 df-nfc 2892 df-ne 2941 df-nel 3047 df-ral 3062 df-rex 3071 df-rmo 3380 df-reu 3381 df-rab 3437 df-v 3482 df-sbc 3789 df-csb 3900 df-dif 3954 df-un 3956 df-in 3958 df-ss 3968 df-pss 3971 df-nul 4334 df-if 4526 df-pw 4602 df-sn 4627 df-pr 4629 df-op 4633 df-uni 4908 df-iun 4993 df-br 5144 df-opab 5206 df-mpt 5226 df-tr 5260 df-id 5578 df-eprel 5584 df-po 5592 df-so 5593 df-fr 5637 df-we 5639 df-xp 5691 df-rel 5692 df-cnv 5693 df-co 5694 df-dm 5695 df-rn 5696 df-res 5697 df-ima 5698 df-pred 6321 df-ord 6387 df-on 6388 df-lim 6389 df-suc 6390 df-iota 6514 df-fun 6563 df-fn 6564 df-f 6565 df-f1 6566 df-fo 6567 df-f1o 6568 df-fv 6569 df-riota 7388 df-ov 7434 df-oprab 7435 df-mpo 7436 df-om 7888 df-1st 8014 df-2nd 8015 df-frecs 8306 df-wrecs 8337 df-recs 8411 df-rdg 8450 df-er 8745 df-map 8868 df-en 8986 df-dom 8987 df-sdom 8988 df-sup 9482 df-inf 9483 df-pnf 11297 df-mnf 11298 df-xr 11299 df-ltxr 11300 df-le 11301 df-sub 11494 df-neg 11495 df-div 11921 df-nn 12267 df-2 12329 df-n0 12527 df-z 12614 df-uz 12879 df-q 12991 df-rp 13035 df-xneg 13154 df-xadd 13155 df-xmul 13156 df-topgen 17488 df-psmet 21356 df-xmet 21357 df-met 21358 df-bl 21359 df-mopn 21360 df-bases 22953 | 
| This theorem is referenced by: equivcmet 25351 | 
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