Metamath Proof Explorer


Theorem ioorinv2

Description: The function F is an "inverse" of sorts to the open interval function. (Contributed by Mario Carneiro, 26-Mar-2015) (Revised by AV, 13-Sep-2020)

Ref Expression
Hypothesis ioorf.1
|- F = ( x e. ran (,) |-> if ( x = (/) , <. 0 , 0 >. , <. inf ( x , RR* , < ) , sup ( x , RR* , < ) >. ) )
Assertion ioorinv2
|- ( ( A (,) B ) =/= (/) -> ( F ` ( A (,) B ) ) = <. A , B >. )

Proof

Step Hyp Ref Expression
1 ioorf.1
 |-  F = ( x e. ran (,) |-> if ( x = (/) , <. 0 , 0 >. , <. inf ( x , RR* , < ) , sup ( x , RR* , < ) >. ) )
2 ioorebas
 |-  ( A (,) B ) e. ran (,)
3 1 ioorval
 |-  ( ( A (,) B ) e. ran (,) -> ( F ` ( A (,) B ) ) = if ( ( A (,) B ) = (/) , <. 0 , 0 >. , <. inf ( ( A (,) B ) , RR* , < ) , sup ( ( A (,) B ) , RR* , < ) >. ) )
4 2 3 ax-mp
 |-  ( F ` ( A (,) B ) ) = if ( ( A (,) B ) = (/) , <. 0 , 0 >. , <. inf ( ( A (,) B ) , RR* , < ) , sup ( ( A (,) B ) , RR* , < ) >. )
5 ifnefalse
 |-  ( ( A (,) B ) =/= (/) -> if ( ( A (,) B ) = (/) , <. 0 , 0 >. , <. inf ( ( A (,) B ) , RR* , < ) , sup ( ( A (,) B ) , RR* , < ) >. ) = <. inf ( ( A (,) B ) , RR* , < ) , sup ( ( A (,) B ) , RR* , < ) >. )
6 n0
 |-  ( ( A (,) B ) =/= (/) <-> E. x x e. ( A (,) B ) )
7 eliooxr
 |-  ( x e. ( A (,) B ) -> ( A e. RR* /\ B e. RR* ) )
8 7 exlimiv
 |-  ( E. x x e. ( A (,) B ) -> ( A e. RR* /\ B e. RR* ) )
9 6 8 sylbi
 |-  ( ( A (,) B ) =/= (/) -> ( A e. RR* /\ B e. RR* ) )
10 9 simpld
 |-  ( ( A (,) B ) =/= (/) -> A e. RR* )
11 9 simprd
 |-  ( ( A (,) B ) =/= (/) -> B e. RR* )
12 id
 |-  ( ( A (,) B ) =/= (/) -> ( A (,) B ) =/= (/) )
13 df-ioo
 |-  (,) = ( x e. RR* , y e. RR* |-> { z e. RR* | ( x < z /\ z < y ) } )
14 idd
 |-  ( ( w e. RR* /\ B e. RR* ) -> ( w < B -> w < B ) )
15 xrltle
 |-  ( ( w e. RR* /\ B e. RR* ) -> ( w < B -> w <_ B ) )
16 idd
 |-  ( ( A e. RR* /\ w e. RR* ) -> ( A < w -> A < w ) )
17 xrltle
 |-  ( ( A e. RR* /\ w e. RR* ) -> ( A < w -> A <_ w ) )
18 13 14 15 16 17 ixxlb
 |-  ( ( A e. RR* /\ B e. RR* /\ ( A (,) B ) =/= (/) ) -> inf ( ( A (,) B ) , RR* , < ) = A )
19 10 11 12 18 syl3anc
 |-  ( ( A (,) B ) =/= (/) -> inf ( ( A (,) B ) , RR* , < ) = A )
20 13 14 15 16 17 ixxub
 |-  ( ( A e. RR* /\ B e. RR* /\ ( A (,) B ) =/= (/) ) -> sup ( ( A (,) B ) , RR* , < ) = B )
21 10 11 12 20 syl3anc
 |-  ( ( A (,) B ) =/= (/) -> sup ( ( A (,) B ) , RR* , < ) = B )
22 19 21 opeq12d
 |-  ( ( A (,) B ) =/= (/) -> <. inf ( ( A (,) B ) , RR* , < ) , sup ( ( A (,) B ) , RR* , < ) >. = <. A , B >. )
23 5 22 eqtrd
 |-  ( ( A (,) B ) =/= (/) -> if ( ( A (,) B ) = (/) , <. 0 , 0 >. , <. inf ( ( A (,) B ) , RR* , < ) , sup ( ( A (,) B ) , RR* , < ) >. ) = <. A , B >. )
24 4 23 syl5eq
 |-  ( ( A (,) B ) =/= (/) -> ( F ` ( A (,) B ) ) = <. A , B >. )