Step |
Hyp |
Ref |
Expression |
1 |
|
breq |
|- ( A = B -> ( u A x <-> u B x ) ) |
2 |
|
breq |
|- ( A = B -> ( u A y <-> u B y ) ) |
3 |
1 2
|
anbi12d |
|- ( A = B -> ( ( u A x /\ u A y ) <-> ( u B x /\ u B y ) ) ) |
4 |
3
|
exbidv |
|- ( A = B -> ( E. u ( u A x /\ u A y ) <-> E. u ( u B x /\ u B y ) ) ) |
5 |
4
|
opabbidv |
|- ( A = B -> { <. x , y >. | E. u ( u A x /\ u A y ) } = { <. x , y >. | E. u ( u B x /\ u B y ) } ) |
6 |
|
df-coss |
|- ,~ A = { <. x , y >. | E. u ( u A x /\ u A y ) } |
7 |
|
df-coss |
|- ,~ B = { <. x , y >. | E. u ( u B x /\ u B y ) } |
8 |
5 6 7
|
3eqtr4g |
|- ( A = B -> ,~ A = ,~ B ) |