Theorem npnflt 9591

Description: An extended real is less than plus infinity iff they are not equal. (Contributed by Jim Kingdon, 17-Apr-2023.)

Assertion

Ref	Expression
npnflt	|- ( A e. RR* -> ( A < +oo <-> A =/= +oo ) )

Proof of Theorem npnflt

Step	Hyp	Ref	Expression
1		nltpnft 9590	. . . 4 |- ( A e. RR* -> ( A = +oo <-> -. A < +oo ) )
2	1	biimpd 143	. . 3 |- ( A e. RR* -> ( A = +oo -> -. A < +oo ) )
3	2	necon2ad 2363	. 2 |- ( A e. RR* -> ( A < +oo -> A =/= +oo ) )
4		ltpnf 9560	. . . . 5 |- ( A e. RR -> A < +oo )
5	4	adantl 275	. . . 4 |- ( ( ( A e. RR* /\ A =/= +oo ) /\ A e. RR ) -> A < +oo )
6		simpr 109	. . . . 5 |- ( ( ( A e. RR* /\ A =/= +oo ) /\ A = +oo ) -> A = +oo )
7		simplr 519	. . . . 5 |- ( ( ( A e. RR* /\ A =/= +oo ) /\ A = +oo ) -> A =/= +oo )
8	6, 7	pm2.21ddne 2389	. . . 4 |- ( ( ( A e. RR* /\ A =/= +oo ) /\ A = +oo ) -> A < +oo )
9		mnfltpnf 9564	. . . . . 6 |- -oo < +oo
10		breq1 3927	. . . . . 6 |- ( A = -oo -> ( A < +oo <-> -oo < +oo ) )
11	9, 10	mpbiri 167	. . . . 5 |- ( A = -oo -> A < +oo )
12	11	adantl 275	. . . 4 |- ( ( ( A e. RR* /\ A =/= +oo ) /\ A = -oo ) -> A < +oo )
13		elxr 9556	. . . . . 6 |- ( A e. RR* <-> ( A e. RR \/ A = +oo \/ A = -oo ) )
14	13	biimpi 119	. . . . 5 |- ( A e. RR* -> ( A e. RR \/ A = +oo \/ A = -oo ) )
15	14	adantr 274	. . . 4 |- ( ( A e. RR* /\ A =/= +oo ) -> ( A e. RR \/ A = +oo \/ A = -oo ) )
16	5, 8, 12, 15	mpjao3dan 1285	. . 3 |- ( ( A e. RR* /\ A =/= +oo ) -> A < +oo )
17	16	ex 114	. 2 |- ( A e. RR* -> ( A =/= +oo -> A < +oo ) )
18	3, 17	impbid 128	1 |- ( A e. RR* -> ( A < +oo <-> A =/= +oo ) )

Syntax hints:   -. wn 3   -> wi 4   /\ wa 103   <-> wb 104   \/ w3o 961   = wceq 1331   e. wcel 1480   =/= wne 2306   class class class wbr 3924   RRcr 7612   +oocpnf 7790   -oocmnf 7791   RR*cxr 7792   < clt 7793

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-in1 603  ax-in2 604  ax-io 698  ax-5 1423  ax-7 1424  ax-gen 1425  ax-ie1 1469  ax-ie2 1470  ax-8 1482  ax-10 1483  ax-11 1484  ax-i12 1485  ax-bndl 1486  ax-4 1487  ax-13 1491  ax-14 1492  ax-17 1506  ax-i9 1510  ax-ial 1514  ax-i5r 1515  ax-ext 2119  ax-sep 4041  ax-pow 4093  ax-pr 4126  ax-un 4350  ax-setind 4447  ax-cnex 7704  ax-resscn 7705  ax-pre-ltirr 7725

This theorem depends on definitions:  df-bi 116  df-3or 963  df-3an 964  df-tru 1334  df-fal 1337  df-nf 1437  df-sb 1736  df-eu 2000  df-mo 2001  df-clab 2124  df-cleq 2130  df-clel 2133  df-nfc 2268  df-ne 2307  df-nel 2402  df-ral 2419  df-rex 2420  df-rab 2423  df-v 2683  df-dif 3068  df-un 3070  df-in 3072  df-ss 3079  df-pw 3507  df-sn 3528  df-pr 3529  df-op 3531  df-uni 3732  df-br 3925  df-opab 3985  df-xp 4540  df-pnf 7795  df-mnf 7796  df-xr 7797  df-ltxr 7798

This theorem is referenced by:  xlt2add  9656  xrmaxadd  11023