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 ) ) ) |
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 ) ) ) |