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Theorem nltpnft 9277
Description: An extended real is not less than plus infinity iff they are equal. (Contributed by NM, 30-Jan-2006.)
Assertion
Ref Expression
nltpnft  |-  ( A  e.  RR*  ->  ( A  = +oo  <->  -.  A  < +oo ) )

Proof of Theorem nltpnft
StepHypRef Expression
1 elxr 9245 . 2  |-  ( A  e.  RR*  <->  ( A  e.  RR  \/  A  = +oo  \/  A  = -oo ) )
2 renepnf 7533 . . . . 5  |-  ( A  e.  RR  ->  A  =/= +oo )
32neneqd 2276 . . . 4  |-  ( A  e.  RR  ->  -.  A  = +oo )
4 ltpnf 9249 . . . . 5  |-  ( A  e.  RR  ->  A  < +oo )
5 notnot 594 . . . . 5  |-  ( A  < +oo  ->  -.  -.  A  < +oo )
64, 5syl 14 . . . 4  |-  ( A  e.  RR  ->  -.  -.  A  < +oo )
73, 62falsed 653 . . 3  |-  ( A  e.  RR  ->  ( A  = +oo  <->  -.  A  < +oo ) )
8 id 19 . . . 4  |-  ( A  = +oo  ->  A  = +oo )
9 pnfxr 7538 . . . . . 6  |- +oo  e.  RR*
10 xrltnr 9248 . . . . . 6  |-  ( +oo  e.  RR*  ->  -. +oo  < +oo )
119, 10ax-mp 7 . . . . 5  |-  -. +oo  < +oo
12 breq1 3848 . . . . 5  |-  ( A  = +oo  ->  ( A  < +oo  <-> +oo  < +oo )
)
1311, 12mtbiri 635 . . . 4  |-  ( A  = +oo  ->  -.  A  < +oo )
148, 132thd 173 . . 3  |-  ( A  = +oo  ->  ( A  = +oo  <->  -.  A  < +oo ) )
15 mnfnepnf 7541 . . . . . 6  |- -oo  =/= +oo
1615neii 2257 . . . . 5  |-  -. -oo  = +oo
17 eqeq1 2094 . . . . 5  |-  ( A  = -oo  ->  ( A  = +oo  <-> -oo  = +oo ) )
1816, 17mtbiri 635 . . . 4  |-  ( A  = -oo  ->  -.  A  = +oo )
19 mnfltpnf 9253 . . . . . . 7  |- -oo  < +oo
20 breq1 3848 . . . . . . 7  |-  ( A  = -oo  ->  ( A  < +oo  <-> -oo  < +oo )
)
2119, 20mpbiri 166 . . . . . 6  |-  ( A  = -oo  ->  A  < +oo )
2221necon3bi 2305 . . . . 5  |-  ( -.  A  < +oo  ->  A  =/= -oo )
2322necon2bi 2310 . . . 4  |-  ( A  = -oo  ->  -.  -.  A  < +oo )
2418, 232falsed 653 . . 3  |-  ( A  = -oo  ->  ( A  = +oo  <->  -.  A  < +oo ) )
257, 14, 243jaoi 1239 . 2  |-  ( ( A  e.  RR  \/  A  = +oo  \/  A  = -oo )  ->  ( A  = +oo  <->  -.  A  < +oo ) )
261, 25sylbi 119 1  |-  ( A  e.  RR*  ->  ( A  = +oo  <->  -.  A  < +oo ) )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4    <-> wb 103    \/ w3o 923    = wceq 1289    e. wcel 1438   class class class wbr 3845   RRcr 7347   +oocpnf 7517   -oocmnf 7518   RR*cxr 7519    < clt 7520
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-in1 579  ax-in2 580  ax-io 665  ax-5 1381  ax-7 1382  ax-gen 1383  ax-ie1 1427  ax-ie2 1428  ax-8 1440  ax-10 1441  ax-11 1442  ax-i12 1443  ax-bndl 1444  ax-4 1445  ax-13 1449  ax-14 1450  ax-17 1464  ax-i9 1468  ax-ial 1472  ax-i5r 1473  ax-ext 2070  ax-sep 3957  ax-pow 4009  ax-pr 4036  ax-un 4260  ax-setind 4353  ax-cnex 7434  ax-resscn 7435  ax-pre-ltirr 7455
This theorem depends on definitions:  df-bi 115  df-3or 925  df-3an 926  df-tru 1292  df-fal 1295  df-nf 1395  df-sb 1693  df-eu 1951  df-mo 1952  df-clab 2075  df-cleq 2081  df-clel 2084  df-nfc 2217  df-ne 2256  df-nel 2351  df-ral 2364  df-rex 2365  df-rab 2368  df-v 2621  df-dif 3001  df-un 3003  df-in 3005  df-ss 3012  df-pw 3431  df-sn 3452  df-pr 3453  df-op 3455  df-uni 3654  df-br 3846  df-opab 3900  df-xp 4444  df-pnf 7522  df-mnf 7523  df-xr 7524  df-ltxr 7525
This theorem is referenced by: (None)
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