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Theorem monsect 15034
Description: If  F is a monomorphism and  G is a section of  F, then  G is an inverse of  F and they are both isomorphisms. This is also stated as "a monomorphism which is also a split epimorphism is an isomorphism". (Contributed by Mario Carneiro, 3-Jan-2017.)
Hypotheses
Ref Expression
sectmon.b  |-  B  =  ( Base `  C
)
sectmon.m  |-  M  =  (Mono `  C )
sectmon.s  |-  S  =  (Sect `  C )
sectmon.c  |-  ( ph  ->  C  e.  Cat )
sectmon.x  |-  ( ph  ->  X  e.  B )
sectmon.y  |-  ( ph  ->  Y  e.  B )
monsect.n  |-  N  =  (Inv `  C )
monsect.1  |-  ( ph  ->  F  e.  ( X M Y ) )
monsect.2  |-  ( ph  ->  G ( Y S X ) F )
Assertion
Ref Expression
monsect  |-  ( ph  ->  F ( X N Y ) G )

Proof of Theorem monsect
StepHypRef Expression
1 monsect.2 . . . . . . . 8  |-  ( ph  ->  G ( Y S X ) F )
2 sectmon.b . . . . . . . . 9  |-  B  =  ( Base `  C
)
3 eqid 2467 . . . . . . . . 9  |-  ( Hom  `  C )  =  ( Hom  `  C )
4 eqid 2467 . . . . . . . . 9  |-  (comp `  C )  =  (comp `  C )
5 eqid 2467 . . . . . . . . 9  |-  ( Id
`  C )  =  ( Id `  C
)
6 sectmon.s . . . . . . . . 9  |-  S  =  (Sect `  C )
7 sectmon.c . . . . . . . . 9  |-  ( ph  ->  C  e.  Cat )
8 sectmon.y . . . . . . . . 9  |-  ( ph  ->  Y  e.  B )
9 sectmon.x . . . . . . . . 9  |-  ( ph  ->  X  e.  B )
102, 3, 4, 5, 6, 7, 8, 9issect 15009 . . . . . . . 8  |-  ( ph  ->  ( G ( Y S X ) F  <-> 
( G  e.  ( Y ( Hom  `  C
) X )  /\  F  e.  ( X
( Hom  `  C ) Y )  /\  ( F ( <. Y ,  X >. (comp `  C
) Y ) G )  =  ( ( Id `  C ) `
 Y ) ) ) )
111, 10mpbid 210 . . . . . . 7  |-  ( ph  ->  ( G  e.  ( Y ( Hom  `  C
) X )  /\  F  e.  ( X
( Hom  `  C ) Y )  /\  ( F ( <. Y ,  X >. (comp `  C
) Y ) G )  =  ( ( Id `  C ) `
 Y ) ) )
1211simp3d 1010 . . . . . 6  |-  ( ph  ->  ( F ( <. Y ,  X >. (comp `  C ) Y ) G )  =  ( ( Id `  C
) `  Y )
)
1312oveq1d 6299 . . . . 5  |-  ( ph  ->  ( ( F (
<. Y ,  X >. (comp `  C ) Y ) G ) ( <. X ,  Y >. (comp `  C ) Y ) F )  =  ( ( ( Id `  C ) `  Y
) ( <. X ,  Y >. (comp `  C
) Y ) F ) )
1411simp2d 1009 . . . . . 6  |-  ( ph  ->  F  e.  ( X ( Hom  `  C
) Y ) )
1511simp1d 1008 . . . . . 6  |-  ( ph  ->  G  e.  ( Y ( Hom  `  C
) X ) )
162, 3, 4, 7, 9, 8, 9, 14, 15, 8, 14catass 14941 . . . . 5  |-  ( ph  ->  ( ( F (
<. Y ,  X >. (comp `  C ) Y ) G ) ( <. X ,  Y >. (comp `  C ) Y ) F )  =  ( F ( <. X ,  X >. (comp `  C
) Y ) ( G ( <. X ,  Y >. (comp `  C
) X ) F ) ) )
172, 3, 5, 7, 9, 4, 8, 14catlid 14938 . . . . . 6  |-  ( ph  ->  ( ( ( Id
`  C ) `  Y ) ( <. X ,  Y >. (comp `  C ) Y ) F )  =  F )
182, 3, 5, 7, 9, 4, 8, 14catrid 14939 . . . . . 6  |-  ( ph  ->  ( F ( <. X ,  X >. (comp `  C ) Y ) ( ( Id `  C ) `  X
) )  =  F )
1917, 18eqtr4d 2511 . . . . 5  |-  ( ph  ->  ( ( ( Id
`  C ) `  Y ) ( <. X ,  Y >. (comp `  C ) Y ) F )  =  ( F ( <. X ,  X >. (comp `  C
) Y ) ( ( Id `  C
) `  X )
) )
2013, 16, 193eqtr3d 2516 . . . 4  |-  ( ph  ->  ( F ( <. X ,  X >. (comp `  C ) Y ) ( G ( <. X ,  Y >. (comp `  C ) X ) F ) )  =  ( F ( <. X ,  X >. (comp `  C ) Y ) ( ( Id `  C ) `  X
) ) )
21 sectmon.m . . . . 5  |-  M  =  (Mono `  C )
22 monsect.1 . . . . 5  |-  ( ph  ->  F  e.  ( X M Y ) )
232, 3, 4, 7, 9, 8, 9, 14, 15catcocl 14940 . . . . 5  |-  ( ph  ->  ( G ( <. X ,  Y >. (comp `  C ) X ) F )  e.  ( X ( Hom  `  C
) X ) )
242, 3, 5, 7, 9catidcl 14937 . . . . 5  |-  ( ph  ->  ( ( Id `  C ) `  X
)  e.  ( X ( Hom  `  C
) X ) )
252, 3, 4, 21, 7, 9, 8, 9, 22, 23, 24moni 14992 . . . 4  |-  ( ph  ->  ( ( F (
<. X ,  X >. (comp `  C ) Y ) ( G ( <. X ,  Y >. (comp `  C ) X ) F ) )  =  ( F ( <. X ,  X >. (comp `  C ) Y ) ( ( Id `  C ) `  X
) )  <->  ( G
( <. X ,  Y >. (comp `  C ) X ) F )  =  ( ( Id
`  C ) `  X ) ) )
2620, 25mpbid 210 . . 3  |-  ( ph  ->  ( G ( <. X ,  Y >. (comp `  C ) X ) F )  =  ( ( Id `  C
) `  X )
)
272, 3, 4, 5, 6, 7, 9, 8, 14, 15issect2 15010 . . 3  |-  ( ph  ->  ( F ( X S Y ) G  <-> 
( G ( <. X ,  Y >. (comp `  C ) X ) F )  =  ( ( Id `  C
) `  X )
) )
2826, 27mpbird 232 . 2  |-  ( ph  ->  F ( X S Y ) G )
29 monsect.n . . 3  |-  N  =  (Inv `  C )
302, 29, 7, 9, 8, 6isinv 15015 . 2  |-  ( ph  ->  ( F ( X N Y ) G  <-> 
( F ( X S Y ) G  /\  G ( Y S X ) F ) ) )
3128, 1, 30mpbir2and 920 1  |-  ( ph  ->  F ( X N Y ) G )
Colors of variables: wff setvar class
Syntax hints:    -> wi 4    /\ w3a 973    = wceq 1379    e. wcel 1767   <.cop 4033   class class class wbr 4447   ` cfv 5588  (class class class)co 6284   Basecbs 14490   Hom chom 14566  compcco 14567   Catccat 14919   Idccid 14920  Monocmon 14984  Sectcsect 15000  Invcinv 15001
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1601  ax-4 1612  ax-5 1680  ax-6 1719  ax-7 1739  ax-8 1769  ax-9 1771  ax-10 1786  ax-11 1791  ax-12 1803  ax-13 1968  ax-ext 2445  ax-rep 4558  ax-sep 4568  ax-nul 4576  ax-pow 4625  ax-pr 4686  ax-un 6576
This theorem depends on definitions:  df-bi 185  df-or 370  df-an 371  df-3an 975  df-tru 1382  df-ex 1597  df-nf 1600  df-sb 1712  df-eu 2279  df-mo 2280  df-clab 2453  df-cleq 2459  df-clel 2462  df-nfc 2617  df-ne 2664  df-ral 2819  df-rex 2820  df-reu 2821  df-rmo 2822  df-rab 2823  df-v 3115  df-sbc 3332  df-csb 3436  df-dif 3479  df-un 3481  df-in 3483  df-ss 3490  df-nul 3786  df-if 3940  df-pw 4012  df-sn 4028  df-pr 4030  df-op 4034  df-uni 4246  df-iun 4327  df-br 4448  df-opab 4506  df-mpt 4507  df-id 4795  df-xp 5005  df-rel 5006  df-cnv 5007  df-co 5008  df-dm 5009  df-rn 5010  df-res 5011  df-ima 5012  df-iota 5551  df-fun 5590  df-fn 5591  df-f 5592  df-f1 5593  df-fo 5594  df-f1o 5595  df-fv 5596  df-riota 6245  df-ov 6287  df-oprab 6288  df-mpt2 6289  df-1st 6784  df-2nd 6785  df-cat 14923  df-cid 14924  df-mon 14986  df-sect 15003  df-inv 15004
This theorem is referenced by:  episect  15036
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