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Theorem psmet0 22326
Description: The distance function of a pseudometric space is zero if its arguments are equal. (Contributed by Thierry Arnoux, 7-Feb-2018.)
Assertion
Ref Expression
psmet0 ((𝐷 ∈ (PsMet‘𝑋) ∧ 𝐴𝑋) → (𝐴𝐷𝐴) = 0)

Proof of Theorem psmet0
Dummy variables 𝑎 𝑏 𝑐 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 elfvex 6360 . . . . . . . 8 (𝐷 ∈ (PsMet‘𝑋) → 𝑋 ∈ V)
2 ispsmet 22322 . . . . . . . 8 (𝑋 ∈ V → (𝐷 ∈ (PsMet‘𝑋) ↔ (𝐷:(𝑋 × 𝑋)⟶ℝ* ∧ ∀𝑎𝑋 ((𝑎𝐷𝑎) = 0 ∧ ∀𝑏𝑋𝑐𝑋 (𝑎𝐷𝑏) ≤ ((𝑐𝐷𝑎) +𝑒 (𝑐𝐷𝑏))))))
31, 2syl 17 . . . . . . 7 (𝐷 ∈ (PsMet‘𝑋) → (𝐷 ∈ (PsMet‘𝑋) ↔ (𝐷:(𝑋 × 𝑋)⟶ℝ* ∧ ∀𝑎𝑋 ((𝑎𝐷𝑎) = 0 ∧ ∀𝑏𝑋𝑐𝑋 (𝑎𝐷𝑏) ≤ ((𝑐𝐷𝑎) +𝑒 (𝑐𝐷𝑏))))))
43ibi 256 . . . . . 6 (𝐷 ∈ (PsMet‘𝑋) → (𝐷:(𝑋 × 𝑋)⟶ℝ* ∧ ∀𝑎𝑋 ((𝑎𝐷𝑎) = 0 ∧ ∀𝑏𝑋𝑐𝑋 (𝑎𝐷𝑏) ≤ ((𝑐𝐷𝑎) +𝑒 (𝑐𝐷𝑏)))))
54simprd 483 . . . . 5 (𝐷 ∈ (PsMet‘𝑋) → ∀𝑎𝑋 ((𝑎𝐷𝑎) = 0 ∧ ∀𝑏𝑋𝑐𝑋 (𝑎𝐷𝑏) ≤ ((𝑐𝐷𝑎) +𝑒 (𝑐𝐷𝑏))))
65r19.21bi 3081 . . . 4 ((𝐷 ∈ (PsMet‘𝑋) ∧ 𝑎𝑋) → ((𝑎𝐷𝑎) = 0 ∧ ∀𝑏𝑋𝑐𝑋 (𝑎𝐷𝑏) ≤ ((𝑐𝐷𝑎) +𝑒 (𝑐𝐷𝑏))))
76simpld 482 . . 3 ((𝐷 ∈ (PsMet‘𝑋) ∧ 𝑎𝑋) → (𝑎𝐷𝑎) = 0)
87ralrimiva 3115 . 2 (𝐷 ∈ (PsMet‘𝑋) → ∀𝑎𝑋 (𝑎𝐷𝑎) = 0)
9 id 22 . . . . 5 (𝑎 = 𝐴𝑎 = 𝐴)
109, 9oveq12d 6809 . . . 4 (𝑎 = 𝐴 → (𝑎𝐷𝑎) = (𝐴𝐷𝐴))
1110eqeq1d 2773 . . 3 (𝑎 = 𝐴 → ((𝑎𝐷𝑎) = 0 ↔ (𝐴𝐷𝐴) = 0))
1211rspcv 3456 . 2 (𝐴𝑋 → (∀𝑎𝑋 (𝑎𝐷𝑎) = 0 → (𝐴𝐷𝐴) = 0))
138, 12mpan9 496 1 ((𝐷 ∈ (PsMet‘𝑋) ∧ 𝐴𝑋) → (𝐴𝐷𝐴) = 0)
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 196  wa 382   = wceq 1631  wcel 2145  wral 3061  Vcvv 3351   class class class wbr 4786   × cxp 5247  wf 6025  cfv 6029  (class class class)co 6791  0cc0 10136  *cxr 10273  cle 10275   +𝑒 cxad 12142  PsMetcpsmet 19938
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1870  ax-4 1885  ax-5 1991  ax-6 2057  ax-7 2093  ax-8 2147  ax-9 2154  ax-10 2174  ax-11 2190  ax-12 2203  ax-13 2408  ax-ext 2751  ax-sep 4915  ax-nul 4923  ax-pow 4974  ax-pr 5034  ax-un 7094  ax-cnex 10192  ax-resscn 10193
This theorem depends on definitions:  df-bi 197  df-an 383  df-or 837  df-3an 1073  df-tru 1634  df-ex 1853  df-nf 1858  df-sb 2050  df-eu 2622  df-mo 2623  df-clab 2758  df-cleq 2764  df-clel 2767  df-nfc 2902  df-ne 2944  df-ral 3066  df-rex 3067  df-rab 3070  df-v 3353  df-sbc 3588  df-dif 3726  df-un 3728  df-in 3730  df-ss 3737  df-nul 4064  df-if 4226  df-pw 4299  df-sn 4317  df-pr 4319  df-op 4323  df-uni 4575  df-br 4787  df-opab 4847  df-mpt 4864  df-id 5157  df-xp 5255  df-rel 5256  df-cnv 5257  df-co 5258  df-dm 5259  df-rn 5260  df-iota 5992  df-fun 6031  df-fn 6032  df-f 6033  df-fv 6037  df-ov 6794  df-oprab 6795  df-mpt2 6796  df-map 8009  df-xr 10278  df-psmet 19946
This theorem is referenced by:  psmetsym  22328  psmetge0  22330  psmetres2  22332  distspace  22334  xblcntrps  22428  ssblps  22440  metustid  22572  metider  30270  pstmfval  30272
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