| Step |
Hyp |
Ref |
Expression |
| 1 |
|
smfval.4 |
|- S = ( .sOLD ` U ) |
| 2 |
|
df-sm |
|- .sOLD = ( 2nd o. 1st ) |
| 3 |
2
|
fveq1i |
|- ( .sOLD ` U ) = ( ( 2nd o. 1st ) ` U ) |
| 4 |
|
fo1st |
|- 1st : _V -onto-> _V |
| 5 |
|
fof |
|- ( 1st : _V -onto-> _V -> 1st : _V --> _V ) |
| 6 |
4 5
|
ax-mp |
|- 1st : _V --> _V |
| 7 |
|
fvco3 |
|- ( ( 1st : _V --> _V /\ U e. _V ) -> ( ( 2nd o. 1st ) ` U ) = ( 2nd ` ( 1st ` U ) ) ) |
| 8 |
6 7
|
mpan |
|- ( U e. _V -> ( ( 2nd o. 1st ) ` U ) = ( 2nd ` ( 1st ` U ) ) ) |
| 9 |
3 8
|
eqtrid |
|- ( U e. _V -> ( .sOLD ` U ) = ( 2nd ` ( 1st ` U ) ) ) |
| 10 |
|
fvprc |
|- ( -. U e. _V -> ( .sOLD ` U ) = (/) ) |
| 11 |
|
fvprc |
|- ( -. U e. _V -> ( 1st ` U ) = (/) ) |
| 12 |
11
|
fveq2d |
|- ( -. U e. _V -> ( 2nd ` ( 1st ` U ) ) = ( 2nd ` (/) ) ) |
| 13 |
|
2nd0 |
|- ( 2nd ` (/) ) = (/) |
| 14 |
12 13
|
eqtr2di |
|- ( -. U e. _V -> (/) = ( 2nd ` ( 1st ` U ) ) ) |
| 15 |
10 14
|
eqtrd |
|- ( -. U e. _V -> ( .sOLD ` U ) = ( 2nd ` ( 1st ` U ) ) ) |
| 16 |
9 15
|
pm2.61i |
|- ( .sOLD ` U ) = ( 2nd ` ( 1st ` U ) ) |
| 17 |
1 16
|
eqtri |
|- S = ( 2nd ` ( 1st ` U ) ) |