| Step | Hyp | Ref | Expression | 
						
							| 1 |  | rngcsectALTV.c |  |-  C = ( RngCatALTV ` U ) | 
						
							| 2 |  | rngcsectALTV.b |  |-  B = ( Base ` C ) | 
						
							| 3 |  | rngcsectALTV.u |  |-  ( ph -> U e. V ) | 
						
							| 4 |  | rngcsectALTV.x |  |-  ( ph -> X e. B ) | 
						
							| 5 |  | rngcsectALTV.y |  |-  ( ph -> Y e. B ) | 
						
							| 6 |  | rngcisoALTV.n |  |-  I = ( Iso ` C ) | 
						
							| 7 |  | eqid |  |-  ( Inv ` C ) = ( Inv ` C ) | 
						
							| 8 | 1 | rngccatALTV |  |-  ( U e. V -> C e. Cat ) | 
						
							| 9 | 3 8 | syl |  |-  ( ph -> C e. Cat ) | 
						
							| 10 | 2 7 9 4 5 6 | isoval |  |-  ( ph -> ( X I Y ) = dom ( X ( Inv ` C ) Y ) ) | 
						
							| 11 | 10 | eleq2d |  |-  ( ph -> ( F e. ( X I Y ) <-> F e. dom ( X ( Inv ` C ) Y ) ) ) | 
						
							| 12 | 2 7 9 4 5 | invfun |  |-  ( ph -> Fun ( X ( Inv ` C ) Y ) ) | 
						
							| 13 |  | funfvbrb |  |-  ( Fun ( X ( Inv ` C ) Y ) -> ( F e. dom ( X ( Inv ` C ) Y ) <-> F ( X ( Inv ` C ) Y ) ( ( X ( Inv ` C ) Y ) ` F ) ) ) | 
						
							| 14 | 12 13 | syl |  |-  ( ph -> ( F e. dom ( X ( Inv ` C ) Y ) <-> F ( X ( Inv ` C ) Y ) ( ( X ( Inv ` C ) Y ) ` F ) ) ) | 
						
							| 15 | 1 2 3 4 5 7 | rngcinvALTV |  |-  ( ph -> ( F ( X ( Inv ` C ) Y ) ( ( X ( Inv ` C ) Y ) ` F ) <-> ( F e. ( X RngIso Y ) /\ ( ( X ( Inv ` C ) Y ) ` F ) = `' F ) ) ) | 
						
							| 16 |  | simpl |  |-  ( ( F e. ( X RngIso Y ) /\ ( ( X ( Inv ` C ) Y ) ` F ) = `' F ) -> F e. ( X RngIso Y ) ) | 
						
							| 17 | 15 16 | biimtrdi |  |-  ( ph -> ( F ( X ( Inv ` C ) Y ) ( ( X ( Inv ` C ) Y ) ` F ) -> F e. ( X RngIso Y ) ) ) | 
						
							| 18 | 14 17 | sylbid |  |-  ( ph -> ( F e. dom ( X ( Inv ` C ) Y ) -> F e. ( X RngIso Y ) ) ) | 
						
							| 19 |  | eqid |  |-  `' F = `' F | 
						
							| 20 | 1 2 3 4 5 7 | rngcinvALTV |  |-  ( ph -> ( F ( X ( Inv ` C ) Y ) `' F <-> ( F e. ( X RngIso Y ) /\ `' F = `' F ) ) ) | 
						
							| 21 |  | funrel |  |-  ( Fun ( X ( Inv ` C ) Y ) -> Rel ( X ( Inv ` C ) Y ) ) | 
						
							| 22 | 12 21 | syl |  |-  ( ph -> Rel ( X ( Inv ` C ) Y ) ) | 
						
							| 23 |  | releldm |  |-  ( ( Rel ( X ( Inv ` C ) Y ) /\ F ( X ( Inv ` C ) Y ) `' F ) -> F e. dom ( X ( Inv ` C ) Y ) ) | 
						
							| 24 | 23 | ex |  |-  ( Rel ( X ( Inv ` C ) Y ) -> ( F ( X ( Inv ` C ) Y ) `' F -> F e. dom ( X ( Inv ` C ) Y ) ) ) | 
						
							| 25 | 22 24 | syl |  |-  ( ph -> ( F ( X ( Inv ` C ) Y ) `' F -> F e. dom ( X ( Inv ` C ) Y ) ) ) | 
						
							| 26 | 20 25 | sylbird |  |-  ( ph -> ( ( F e. ( X RngIso Y ) /\ `' F = `' F ) -> F e. dom ( X ( Inv ` C ) Y ) ) ) | 
						
							| 27 | 19 26 | mpan2i |  |-  ( ph -> ( F e. ( X RngIso Y ) -> F e. dom ( X ( Inv ` C ) Y ) ) ) | 
						
							| 28 | 18 27 | impbid |  |-  ( ph -> ( F e. dom ( X ( Inv ` C ) Y ) <-> F e. ( X RngIso Y ) ) ) | 
						
							| 29 | 11 28 | bitrd |  |-  ( ph -> ( F e. ( X I Y ) <-> F e. ( X RngIso Y ) ) ) |