Step |
Hyp |
Ref |
Expression |
1 |
|
recn |
|- ( A e. RR -> A e. CC ) |
2 |
|
recn |
|- ( B e. RR -> B e. CC ) |
3 |
|
addcom |
|- ( ( A e. CC /\ B e. CC ) -> ( A + B ) = ( B + A ) ) |
4 |
1 2 3
|
syl2an |
|- ( ( A e. RR /\ B e. RR ) -> ( A + B ) = ( B + A ) ) |
5 |
4
|
3adant3 |
|- ( ( A e. RR /\ B e. RR /\ C e. RR ) -> ( A + B ) = ( B + A ) ) |
6 |
5
|
breq1d |
|- ( ( A e. RR /\ B e. RR /\ C e. RR ) -> ( ( A + B ) <_ C <-> ( B + A ) <_ C ) ) |
7 |
|
leaddsub |
|- ( ( B e. RR /\ A e. RR /\ C e. RR ) -> ( ( B + A ) <_ C <-> B <_ ( C - A ) ) ) |
8 |
7
|
3com12 |
|- ( ( A e. RR /\ B e. RR /\ C e. RR ) -> ( ( B + A ) <_ C <-> B <_ ( C - A ) ) ) |
9 |
6 8
|
bitrd |
|- ( ( A e. RR /\ B e. RR /\ C e. RR ) -> ( ( A + B ) <_ C <-> B <_ ( C - A ) ) ) |