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Description: Value of the first projection on an object. (Contributed by Mario Carneiro, 11-Jan-2017)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | 1stfval.t | |- T = ( C Xc. D ) |
|
| 1stfval.b | |- B = ( Base ` T ) |
||
| 1stfval.h | |- H = ( Hom ` T ) |
||
| 1stfval.c | |- ( ph -> C e. Cat ) |
||
| 1stfval.d | |- ( ph -> D e. Cat ) |
||
| 2ndfval.p | |- Q = ( C 2ndF D ) |
||
| 2ndf1.p | |- ( ph -> R e. B ) |
||
| Assertion | 2ndf1 | |- ( ph -> ( ( 1st ` Q ) ` R ) = ( 2nd ` R ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | 1stfval.t | |- T = ( C Xc. D ) |
|
| 2 | 1stfval.b | |- B = ( Base ` T ) |
|
| 3 | 1stfval.h | |- H = ( Hom ` T ) |
|
| 4 | 1stfval.c | |- ( ph -> C e. Cat ) |
|
| 5 | 1stfval.d | |- ( ph -> D e. Cat ) |
|
| 6 | 2ndfval.p | |- Q = ( C 2ndF D ) |
|
| 7 | 2ndf1.p | |- ( ph -> R e. B ) |
|
| 8 | 1 2 3 4 5 6 | 2ndfval | |- ( ph -> Q = <. ( 2nd |` B ) , ( x e. B , y e. B |-> ( 2nd |` ( x H y ) ) ) >. ) |
| 9 | fo2nd | |- 2nd : _V -onto-> _V |
|
| 10 | fofun | |- ( 2nd : _V -onto-> _V -> Fun 2nd ) |
|
| 11 | 9 10 | ax-mp | |- Fun 2nd |
| 12 | 2 | fvexi | |- B e. _V |
| 13 | resfunexg | |- ( ( Fun 2nd /\ B e. _V ) -> ( 2nd |` B ) e. _V ) |
|
| 14 | 11 12 13 | mp2an | |- ( 2nd |` B ) e. _V |
| 15 | 12 12 | mpoex | |- ( x e. B , y e. B |-> ( 2nd |` ( x H y ) ) ) e. _V |
| 16 | 14 15 | op1std | |- ( Q = <. ( 2nd |` B ) , ( x e. B , y e. B |-> ( 2nd |` ( x H y ) ) ) >. -> ( 1st ` Q ) = ( 2nd |` B ) ) |
| 17 | 8 16 | syl | |- ( ph -> ( 1st ` Q ) = ( 2nd |` B ) ) |
| 18 | 17 | fveq1d | |- ( ph -> ( ( 1st ` Q ) ` R ) = ( ( 2nd |` B ) ` R ) ) |
| 19 | 7 | fvresd | |- ( ph -> ( ( 2nd |` B ) ` R ) = ( 2nd ` R ) ) |
| 20 | 18 19 | eqtrd | |- ( ph -> ( ( 1st ` Q ) ` R ) = ( 2nd ` R ) ) |