| Step | Hyp | Ref | Expression | 
						
							| 1 |  | brco3f1o.c |  |-  ( ph -> C : Y -1-1-onto-> Z ) | 
						
							| 2 |  | brco3f1o.d |  |-  ( ph -> D : X -1-1-onto-> Y ) | 
						
							| 3 |  | brco3f1o.e |  |-  ( ph -> E : W -1-1-onto-> X ) | 
						
							| 4 |  | brco3f1o.r |  |-  ( ph -> A ( C o. ( D o. E ) ) B ) | 
						
							| 5 |  | f1ocnv |  |-  ( E : W -1-1-onto-> X -> `' E : X -1-1-onto-> W ) | 
						
							| 6 |  | f1ofn |  |-  ( `' E : X -1-1-onto-> W -> `' E Fn X ) | 
						
							| 7 | 3 5 6 | 3syl |  |-  ( ph -> `' E Fn X ) | 
						
							| 8 |  | f1ocnv |  |-  ( D : X -1-1-onto-> Y -> `' D : Y -1-1-onto-> X ) | 
						
							| 9 |  | f1of |  |-  ( `' D : Y -1-1-onto-> X -> `' D : Y --> X ) | 
						
							| 10 | 2 8 9 | 3syl |  |-  ( ph -> `' D : Y --> X ) | 
						
							| 11 |  | f1ocnv |  |-  ( C : Y -1-1-onto-> Z -> `' C : Z -1-1-onto-> Y ) | 
						
							| 12 |  | f1of |  |-  ( `' C : Z -1-1-onto-> Y -> `' C : Z --> Y ) | 
						
							| 13 | 1 11 12 | 3syl |  |-  ( ph -> `' C : Z --> Y ) | 
						
							| 14 |  | relco |  |-  Rel ( ( C o. D ) o. E ) | 
						
							| 15 | 14 | relbrcnv |  |-  ( B `' ( ( C o. D ) o. E ) A <-> A ( ( C o. D ) o. E ) B ) | 
						
							| 16 |  | cnvco |  |-  `' ( ( C o. D ) o. E ) = ( `' E o. `' ( C o. D ) ) | 
						
							| 17 |  | cnvco |  |-  `' ( C o. D ) = ( `' D o. `' C ) | 
						
							| 18 | 17 | coeq2i |  |-  ( `' E o. `' ( C o. D ) ) = ( `' E o. ( `' D o. `' C ) ) | 
						
							| 19 | 16 18 | eqtri |  |-  `' ( ( C o. D ) o. E ) = ( `' E o. ( `' D o. `' C ) ) | 
						
							| 20 | 19 | breqi |  |-  ( B `' ( ( C o. D ) o. E ) A <-> B ( `' E o. ( `' D o. `' C ) ) A ) | 
						
							| 21 |  | coass |  |-  ( ( C o. D ) o. E ) = ( C o. ( D o. E ) ) | 
						
							| 22 | 21 | breqi |  |-  ( A ( ( C o. D ) o. E ) B <-> A ( C o. ( D o. E ) ) B ) | 
						
							| 23 | 15 20 22 | 3bitr3ri |  |-  ( A ( C o. ( D o. E ) ) B <-> B ( `' E o. ( `' D o. `' C ) ) A ) | 
						
							| 24 | 4 23 | sylib |  |-  ( ph -> B ( `' E o. ( `' D o. `' C ) ) A ) | 
						
							| 25 | 7 10 13 24 | brcofffn |  |-  ( ph -> ( B `' C ( `' C ` B ) /\ ( `' C ` B ) `' D ( `' D ` ( `' C ` B ) ) /\ ( `' D ` ( `' C ` B ) ) `' E A ) ) | 
						
							| 26 |  | f1orel |  |-  ( C : Y -1-1-onto-> Z -> Rel C ) | 
						
							| 27 |  | relbrcnvg |  |-  ( Rel C -> ( B `' C ( `' C ` B ) <-> ( `' C ` B ) C B ) ) | 
						
							| 28 | 1 26 27 | 3syl |  |-  ( ph -> ( B `' C ( `' C ` B ) <-> ( `' C ` B ) C B ) ) | 
						
							| 29 |  | f1orel |  |-  ( D : X -1-1-onto-> Y -> Rel D ) | 
						
							| 30 |  | relbrcnvg |  |-  ( Rel D -> ( ( `' C ` B ) `' D ( `' D ` ( `' C ` B ) ) <-> ( `' D ` ( `' C ` B ) ) D ( `' C ` B ) ) ) | 
						
							| 31 | 2 29 30 | 3syl |  |-  ( ph -> ( ( `' C ` B ) `' D ( `' D ` ( `' C ` B ) ) <-> ( `' D ` ( `' C ` B ) ) D ( `' C ` B ) ) ) | 
						
							| 32 |  | f1orel |  |-  ( E : W -1-1-onto-> X -> Rel E ) | 
						
							| 33 |  | relbrcnvg |  |-  ( Rel E -> ( ( `' D ` ( `' C ` B ) ) `' E A <-> A E ( `' D ` ( `' C ` B ) ) ) ) | 
						
							| 34 | 3 32 33 | 3syl |  |-  ( ph -> ( ( `' D ` ( `' C ` B ) ) `' E A <-> A E ( `' D ` ( `' C ` B ) ) ) ) | 
						
							| 35 | 28 31 34 | 3anbi123d |  |-  ( ph -> ( ( B `' C ( `' C ` B ) /\ ( `' C ` B ) `' D ( `' D ` ( `' C ` B ) ) /\ ( `' D ` ( `' C ` B ) ) `' E A ) <-> ( ( `' C ` B ) C B /\ ( `' D ` ( `' C ` B ) ) D ( `' C ` B ) /\ A E ( `' D ` ( `' C ` B ) ) ) ) ) | 
						
							| 36 | 25 35 | mpbid |  |-  ( ph -> ( ( `' C ` B ) C B /\ ( `' D ` ( `' C ` B ) ) D ( `' C ` B ) /\ A E ( `' D ` ( `' C ` B ) ) ) ) |