| Step | Hyp | Ref | Expression | 
						
							| 1 |  | sbthlem.1 |  |-  A e. _V | 
						
							| 2 |  | sbthlem.2 |  |-  D = { x | ( x C_ A /\ ( g " ( B \ ( f " x ) ) ) C_ ( A \ x ) ) } | 
						
							| 3 | 1 2 | sbthlem1 |  |-  U. D C_ ( A \ ( g " ( B \ ( f " U. D ) ) ) ) | 
						
							| 4 |  | imass2 |  |-  ( U. D C_ ( A \ ( g " ( B \ ( f " U. D ) ) ) ) -> ( f " U. D ) C_ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) | 
						
							| 5 |  | sscon |  |-  ( ( f " U. D ) C_ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) -> ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) C_ ( B \ ( f " U. D ) ) ) | 
						
							| 6 | 3 4 5 | mp2b |  |-  ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) C_ ( B \ ( f " U. D ) ) | 
						
							| 7 |  | imass2 |  |-  ( ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) C_ ( B \ ( f " U. D ) ) -> ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) C_ ( g " ( B \ ( f " U. D ) ) ) ) | 
						
							| 8 |  | sscon |  |-  ( ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) C_ ( g " ( B \ ( f " U. D ) ) ) -> ( A \ ( g " ( B \ ( f " U. D ) ) ) ) C_ ( A \ ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) ) ) | 
						
							| 9 | 6 7 8 | mp2b |  |-  ( A \ ( g " ( B \ ( f " U. D ) ) ) ) C_ ( A \ ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) ) | 
						
							| 10 |  | imassrn |  |-  ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) C_ ran g | 
						
							| 11 |  | sstr2 |  |-  ( ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) C_ ran g -> ( ran g C_ A -> ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) C_ A ) ) | 
						
							| 12 | 10 11 | ax-mp |  |-  ( ran g C_ A -> ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) C_ A ) | 
						
							| 13 |  | difss |  |-  ( A \ ( g " ( B \ ( f " U. D ) ) ) ) C_ A | 
						
							| 14 |  | ssconb |  |-  ( ( ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) C_ A /\ ( A \ ( g " ( B \ ( f " U. D ) ) ) ) C_ A ) -> ( ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) C_ ( A \ ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) <-> ( A \ ( g " ( B \ ( f " U. D ) ) ) ) C_ ( A \ ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) ) ) ) | 
						
							| 15 | 12 13 14 | sylancl |  |-  ( ran g C_ A -> ( ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) C_ ( A \ ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) <-> ( A \ ( g " ( B \ ( f " U. D ) ) ) ) C_ ( A \ ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) ) ) ) | 
						
							| 16 | 9 15 | mpbiri |  |-  ( ran g C_ A -> ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) C_ ( A \ ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) | 
						
							| 17 | 16 13 | jctil |  |-  ( ran g C_ A -> ( ( A \ ( g " ( B \ ( f " U. D ) ) ) ) C_ A /\ ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) C_ ( A \ ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) | 
						
							| 18 | 1 | difexi |  |-  ( A \ ( g " ( B \ ( f " U. D ) ) ) ) e. _V | 
						
							| 19 |  | sseq1 |  |-  ( x = ( A \ ( g " ( B \ ( f " U. D ) ) ) ) -> ( x C_ A <-> ( A \ ( g " ( B \ ( f " U. D ) ) ) ) C_ A ) ) | 
						
							| 20 |  | imaeq2 |  |-  ( x = ( A \ ( g " ( B \ ( f " U. D ) ) ) ) -> ( f " x ) = ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) | 
						
							| 21 | 20 | difeq2d |  |-  ( x = ( A \ ( g " ( B \ ( f " U. D ) ) ) ) -> ( B \ ( f " x ) ) = ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) | 
						
							| 22 | 21 | imaeq2d |  |-  ( x = ( A \ ( g " ( B \ ( f " U. D ) ) ) ) -> ( g " ( B \ ( f " x ) ) ) = ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) ) | 
						
							| 23 |  | difeq2 |  |-  ( x = ( A \ ( g " ( B \ ( f " U. D ) ) ) ) -> ( A \ x ) = ( A \ ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) | 
						
							| 24 | 22 23 | sseq12d |  |-  ( x = ( A \ ( g " ( B \ ( f " U. D ) ) ) ) -> ( ( g " ( B \ ( f " x ) ) ) C_ ( A \ x ) <-> ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) C_ ( A \ ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) | 
						
							| 25 | 19 24 | anbi12d |  |-  ( x = ( A \ ( g " ( B \ ( f " U. D ) ) ) ) -> ( ( x C_ A /\ ( g " ( B \ ( f " x ) ) ) C_ ( A \ x ) ) <-> ( ( A \ ( g " ( B \ ( f " U. D ) ) ) ) C_ A /\ ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) C_ ( A \ ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) ) | 
						
							| 26 | 18 25 | elab |  |-  ( ( A \ ( g " ( B \ ( f " U. D ) ) ) ) e. { x | ( x C_ A /\ ( g " ( B \ ( f " x ) ) ) C_ ( A \ x ) ) } <-> ( ( A \ ( g " ( B \ ( f " U. D ) ) ) ) C_ A /\ ( g " ( B \ ( f " ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) C_ ( A \ ( A \ ( g " ( B \ ( f " U. D ) ) ) ) ) ) ) | 
						
							| 27 | 17 26 | sylibr |  |-  ( ran g C_ A -> ( A \ ( g " ( B \ ( f " U. D ) ) ) ) e. { x | ( x C_ A /\ ( g " ( B \ ( f " x ) ) ) C_ ( A \ x ) ) } ) | 
						
							| 28 | 27 2 | eleqtrrdi |  |-  ( ran g C_ A -> ( A \ ( g " ( B \ ( f " U. D ) ) ) ) e. D ) | 
						
							| 29 |  | elssuni |  |-  ( ( A \ ( g " ( B \ ( f " U. D ) ) ) ) e. D -> ( A \ ( g " ( B \ ( f " U. D ) ) ) ) C_ U. D ) | 
						
							| 30 | 28 29 | syl |  |-  ( ran g C_ A -> ( A \ ( g " ( B \ ( f " U. D ) ) ) ) C_ U. D ) |