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Description: The object part of the diagonal functor is 1-1 if B is non-empty. (Contributed by Zhi Wang, 19-Oct-2025)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | diag1f1.l | |- L = ( C DiagFunc D ) |
|
| diag1f1.c | |- ( ph -> C e. Cat ) |
||
| diag1f1.d | |- ( ph -> D e. Cat ) |
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| diag1f1.a | |- A = ( Base ` C ) |
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| diag1f1.b | |- B = ( Base ` D ) |
||
| diag1f1.0 | |- ( ph -> B =/= (/) ) |
||
| Assertion | diag1f1 | |- ( ph -> ( 1st ` L ) : A -1-1-> ( D Func C ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | diag1f1.l | |- L = ( C DiagFunc D ) |
|
| 2 | diag1f1.c | |- ( ph -> C e. Cat ) |
|
| 3 | diag1f1.d | |- ( ph -> D e. Cat ) |
|
| 4 | diag1f1.a | |- A = ( Base ` C ) |
|
| 5 | diag1f1.b | |- B = ( Base ` D ) |
|
| 6 | diag1f1.0 | |- ( ph -> B =/= (/) ) |
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| 7 | eqid | |- ( D FuncCat C ) = ( D FuncCat C ) |
|
| 8 | 7 | fucbas | |- ( D Func C ) = ( Base ` ( D FuncCat C ) ) |
| 9 | 1 2 3 7 | diagcl | |- ( ph -> L e. ( C Func ( D FuncCat C ) ) ) |
| 10 | 9 | func1st2nd | |- ( ph -> ( 1st ` L ) ( C Func ( D FuncCat C ) ) ( 2nd ` L ) ) |
| 11 | 4 8 10 | funcf1 | |- ( ph -> ( 1st ` L ) : A --> ( D Func C ) ) |
| 12 | 2 | adantr | |- ( ( ph /\ ( x e. A /\ y e. A ) ) -> C e. Cat ) |
| 13 | 3 | adantr | |- ( ( ph /\ ( x e. A /\ y e. A ) ) -> D e. Cat ) |
| 14 | 6 | adantr | |- ( ( ph /\ ( x e. A /\ y e. A ) ) -> B =/= (/) ) |
| 15 | simprl | |- ( ( ph /\ ( x e. A /\ y e. A ) ) -> x e. A ) |
|
| 16 | simprr | |- ( ( ph /\ ( x e. A /\ y e. A ) ) -> y e. A ) |
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| 17 | eqid | |- ( ( 1st ` L ) ` x ) = ( ( 1st ` L ) ` x ) |
|
| 18 | eqid | |- ( ( 1st ` L ) ` y ) = ( ( 1st ` L ) ` y ) |
|
| 19 | 1 12 13 4 5 14 15 16 17 18 | diag1f1lem | |- ( ( ph /\ ( x e. A /\ y e. A ) ) -> ( ( ( 1st ` L ) ` x ) = ( ( 1st ` L ) ` y ) -> x = y ) ) |
| 20 | 19 | ralrimivva | |- ( ph -> A. x e. A A. y e. A ( ( ( 1st ` L ) ` x ) = ( ( 1st ` L ) ` y ) -> x = y ) ) |
| 21 | dff13 | |- ( ( 1st ` L ) : A -1-1-> ( D Func C ) <-> ( ( 1st ` L ) : A --> ( D Func C ) /\ A. x e. A A. y e. A ( ( ( 1st ` L ) ` x ) = ( ( 1st ` L ) ` y ) -> x = y ) ) ) |
|
| 22 | 11 20 21 | sylanbrc | |- ( ph -> ( 1st ` L ) : A -1-1-> ( D Func C ) ) |