Step |
Hyp |
Ref |
Expression |
1 |
|
ssltleft |
|- ( A e. No -> ( _Left ` A ) < |
2 |
|
ssltright |
|- ( A e. No -> { A } < |
3 |
|
snnzg |
|- ( A e. No -> { A } =/= (/) ) |
4 |
|
sslttr |
|- ( ( ( _Left ` A ) < ( _Left ` A ) < |
5 |
1 2 3 4
|
syl3anc |
|- ( A e. No -> ( _Left ` A ) < |
6 |
|
0elpw |
|- (/) e. ~P No |
7 |
|
nulssgt |
|- ( (/) e. ~P No -> (/) < |
8 |
6 7
|
mp1i |
|- ( -. A e. No -> (/) < |
9 |
|
leftf |
|- _Left : No --> ~P No |
10 |
9
|
fdmi |
|- dom _Left = No |
11 |
10
|
eleq2i |
|- ( A e. dom _Left <-> A e. No ) |
12 |
|
ndmfv |
|- ( -. A e. dom _Left -> ( _Left ` A ) = (/) ) |
13 |
11 12
|
sylnbir |
|- ( -. A e. No -> ( _Left ` A ) = (/) ) |
14 |
|
rightf |
|- _Right : No --> ~P No |
15 |
14
|
fdmi |
|- dom _Right = No |
16 |
15
|
eleq2i |
|- ( A e. dom _Right <-> A e. No ) |
17 |
|
ndmfv |
|- ( -. A e. dom _Right -> ( _Right ` A ) = (/) ) |
18 |
16 17
|
sylnbir |
|- ( -. A e. No -> ( _Right ` A ) = (/) ) |
19 |
8 13 18
|
3brtr4d |
|- ( -. A e. No -> ( _Left ` A ) < |
20 |
5 19
|
pm2.61i |
|- ( _Left ` A ) < |