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Theorem elxr 8928
Description: Membership in the set of extended reals. (Contributed by NM, 14-Oct-2005.)
Assertion
Ref Expression
elxr  |-  ( A  e.  RR*  <->  ( A  e.  RR  \/  A  = +oo  \/  A  = -oo ) )

Proof of Theorem elxr
StepHypRef Expression
1 df-xr 7219 . . 3  |-  RR*  =  ( RR  u.  { +oo , -oo } )
21eleq2i 2146 . 2  |-  ( A  e.  RR*  <->  A  e.  ( RR  u.  { +oo , -oo } ) )
3 elun 3114 . 2  |-  ( A  e.  ( RR  u.  { +oo , -oo }
)  <->  ( A  e.  RR  \/  A  e. 
{ +oo , -oo }
) )
4 pnfex 7234 . . . . 5  |- +oo  e.  _V
5 mnfxr 7237 . . . . . 6  |- -oo  e.  RR*
65elexi 2612 . . . . 5  |- -oo  e.  _V
74, 6elpr2 3428 . . . 4  |-  ( A  e.  { +oo , -oo }  <->  ( A  = +oo  \/  A  = -oo ) )
87orbi2i 712 . . 3  |-  ( ( A  e.  RR  \/  A  e.  { +oo , -oo } )  <->  ( A  e.  RR  \/  ( A  = +oo  \/  A  = -oo ) ) )
9 3orass 923 . . 3  |-  ( ( A  e.  RR  \/  A  = +oo  \/  A  = -oo )  <->  ( A  e.  RR  \/  ( A  = +oo  \/  A  = -oo ) ) )
108, 9bitr4i 185 . 2  |-  ( ( A  e.  RR  \/  A  e.  { +oo , -oo } )  <->  ( A  e.  RR  \/  A  = +oo  \/  A  = -oo ) )
112, 3, 103bitri 204 1  |-  ( A  e.  RR*  <->  ( A  e.  RR  \/  A  = +oo  \/  A  = -oo ) )
Colors of variables: wff set class
Syntax hints:    <-> wb 103    \/ wo 662    \/ w3o 919    = wceq 1285    e. wcel 1434    u. cun 2972   {cpr 3407   RRcr 7042   +oocpnf 7212   -oocmnf 7213   RR*cxr 7214
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-io 663  ax-5 1377  ax-7 1378  ax-gen 1379  ax-ie1 1423  ax-ie2 1424  ax-8 1436  ax-10 1437  ax-11 1438  ax-i12 1439  ax-bndl 1440  ax-4 1441  ax-13 1445  ax-14 1446  ax-17 1460  ax-i9 1464  ax-ial 1468  ax-i5r 1469  ax-ext 2064  ax-sep 3904  ax-pow 3956  ax-un 4196  ax-cnex 7129
This theorem depends on definitions:  df-bi 115  df-3or 921  df-tru 1288  df-nf 1391  df-sb 1687  df-clab 2069  df-cleq 2075  df-clel 2078  df-nfc 2209  df-rex 2355  df-v 2604  df-un 2978  df-in 2980  df-ss 2987  df-pw 3392  df-sn 3412  df-pr 3413  df-uni 3610  df-pnf 7217  df-mnf 7218  df-xr 7219
This theorem is referenced by:  xrnemnf  8929  xrnepnf  8930  xrltnr  8931  xrltnsym  8944  xrlttr  8946  xrltso  8947  xrlttri3  8948  nltpnft  8960  ngtmnft  8961  xrrebnd  8962  xnegcl  8975  xnegneg  8976  xltnegi  8978  qbtwnxr  9344
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