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Theorem xmet0 21281
Description: The distance function of a metric space is zero if its arguments are equal. Definition 14-1.1(a) of [Gleason] p. 223. (Contributed by Mario Carneiro, 20-Aug-2015.)
Assertion
Ref Expression
xmet0  |-  ( ( D  e.  ( *Met `  X )  /\  A  e.  X
)  ->  ( A D A )  =  0 )

Proof of Theorem xmet0
StepHypRef Expression
1 eqid 2420 . 2  |-  A  =  A
2 xmeteq0 21277 . . 3  |-  ( ( D  e.  ( *Met `  X )  /\  A  e.  X  /\  A  e.  X
)  ->  ( ( A D A )  =  0  <->  A  =  A
) )
323anidm23 1323 . 2  |-  ( ( D  e.  ( *Met `  X )  /\  A  e.  X
)  ->  ( ( A D A )  =  0  <->  A  =  A
) )
41, 3mpbiri 236 1  |-  ( ( D  e.  ( *Met `  X )  /\  A  e.  X
)  ->  ( A D A )  =  0 )
Colors of variables: wff setvar class
Syntax hints:    -> wi 4    <-> wb 187    /\ wa 370    = wceq 1437    e. wcel 1867   ` cfv 5592  (class class class)co 6296   0cc0 9528   *Metcxmt 18883
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1665  ax-4 1678  ax-5 1748  ax-6 1794  ax-7 1838  ax-8 1869  ax-9 1871  ax-10 1886  ax-11 1891  ax-12 1904  ax-13 2052  ax-ext 2398  ax-sep 4539  ax-nul 4547  ax-pow 4594  ax-pr 4652  ax-un 6588  ax-cnex 9584  ax-resscn 9585
This theorem depends on definitions:  df-bi 188  df-or 371  df-an 372  df-3an 984  df-tru 1440  df-ex 1660  df-nf 1664  df-sb 1787  df-eu 2267  df-mo 2268  df-clab 2406  df-cleq 2412  df-clel 2415  df-nfc 2570  df-ne 2618  df-ral 2778  df-rex 2779  df-rab 2782  df-v 3080  df-sbc 3297  df-dif 3436  df-un 3438  df-in 3440  df-ss 3447  df-nul 3759  df-if 3907  df-pw 3978  df-sn 3994  df-pr 3996  df-op 4000  df-uni 4214  df-br 4418  df-opab 4476  df-mpt 4477  df-id 4760  df-xp 4851  df-rel 4852  df-cnv 4853  df-co 4854  df-dm 4855  df-rn 4856  df-iota 5556  df-fun 5594  df-fn 5595  df-f 5596  df-fv 5600  df-ov 6299  df-oprab 6300  df-mpt2 6301  df-map 7473  df-xr 9668  df-xmet 18891
This theorem is referenced by:  met0  21282  xmetge0  21283  xmetsym  21286  xmetpsmet  21287  xblcntr  21350  ssbl  21362  xmeter  21372  ubthlem2  26384
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