Metamath Proof Explorer


Theorem xeqlelt

Description: Equality in terms of 'less than or equal to', 'less than'. (Contributed by Thierry Arnoux, 5-Jul-2017)

Ref Expression
Assertion xeqlelt
|- ( ( A e. RR* /\ B e. RR* ) -> ( A = B <-> ( A <_ B /\ -. A < B ) ) )

Proof

Step Hyp Ref Expression
1 xrletri3
 |-  ( ( A e. RR* /\ B e. RR* ) -> ( A = B <-> ( A <_ B /\ B <_ A ) ) )
2 xrlenlt
 |-  ( ( B e. RR* /\ A e. RR* ) -> ( B <_ A <-> -. A < B ) )
3 2 ancoms
 |-  ( ( A e. RR* /\ B e. RR* ) -> ( B <_ A <-> -. A < B ) )
4 3 anbi2d
 |-  ( ( A e. RR* /\ B e. RR* ) -> ( ( A <_ B /\ B <_ A ) <-> ( A <_ B /\ -. A < B ) ) )
5 1 4 bitrd
 |-  ( ( A e. RR* /\ B e. RR* ) -> ( A = B <-> ( A <_ B /\ -. A < B ) ) )