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Description: Lemma for fucoppc . (Contributed by Zhi Wang, 18-Nov-2025)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | fucoppclem.o | |- O = ( oppCat ` C ) |
|
| fucoppclem.p | |- P = ( oppCat ` D ) |
||
| fucoppclem.n | |- N = ( C Nat D ) |
||
| fucoppclem.f | |- ( ph -> F = ( oppFunc |` ( C Func D ) ) ) |
||
| fucoppclem.x | |- ( ph -> X e. ( C Func D ) ) |
||
| fucoppclem.y | |- ( ph -> Y e. ( C Func D ) ) |
||
| Assertion | fucoppclem | |- ( ph -> ( Y N X ) = ( ( F ` X ) ( O Nat P ) ( F ` Y ) ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | fucoppclem.o | |- O = ( oppCat ` C ) |
|
| 2 | fucoppclem.p | |- P = ( oppCat ` D ) |
|
| 3 | fucoppclem.n | |- N = ( C Nat D ) |
|
| 4 | fucoppclem.f | |- ( ph -> F = ( oppFunc |` ( C Func D ) ) ) |
|
| 5 | fucoppclem.x | |- ( ph -> X e. ( C Func D ) ) |
|
| 6 | fucoppclem.y | |- ( ph -> Y e. ( C Func D ) ) |
|
| 7 | eqid | |- ( O Nat P ) = ( O Nat P ) |
|
| 8 | 4 | fveq1d | |- ( ph -> ( F ` Y ) = ( ( oppFunc |` ( C Func D ) ) ` Y ) ) |
| 9 | 6 | fvresd | |- ( ph -> ( ( oppFunc |` ( C Func D ) ) ` Y ) = ( oppFunc ` Y ) ) |
| 10 | 8 9 | eqtrd | |- ( ph -> ( F ` Y ) = ( oppFunc ` Y ) ) |
| 11 | 4 | fveq1d | |- ( ph -> ( F ` X ) = ( ( oppFunc |` ( C Func D ) ) ` X ) ) |
| 12 | 5 | fvresd | |- ( ph -> ( ( oppFunc |` ( C Func D ) ) ` X ) = ( oppFunc ` X ) ) |
| 13 | 11 12 | eqtrd | |- ( ph -> ( F ` X ) = ( oppFunc ` X ) ) |
| 14 | 5 | func1st2nd | |- ( ph -> ( 1st ` X ) ( C Func D ) ( 2nd ` X ) ) |
| 15 | 14 | funcrcl2 | |- ( ph -> C e. Cat ) |
| 16 | 14 | funcrcl3 | |- ( ph -> D e. Cat ) |
| 17 | 1 2 3 7 10 13 15 16 | natoppfb | |- ( ph -> ( Y N X ) = ( ( F ` X ) ( O Nat P ) ( F ` Y ) ) ) |