| Step | Hyp | Ref | Expression | 
						
							| 1 |  | upwordsing.1 |  |-  A e. S | 
						
							| 2 |  | s1cl |  |-  ( A e. S -> <" A "> e. Word S ) | 
						
							| 3 |  | elab6g |  |-  ( <" A "> e. Word S -> ( <" A "> e. { w | ( w e. Word S /\ A. k e. ( 0 ..^ ( ( # ` w ) - 1 ) ) ( w ` k ) < ( w ` ( k + 1 ) ) ) } <-> A. w ( w = <" A "> -> ( w e. Word S /\ A. k e. ( 0 ..^ ( ( # ` w ) - 1 ) ) ( w ` k ) < ( w ` ( k + 1 ) ) ) ) ) ) | 
						
							| 4 | 1 2 3 | mp2b |  |-  ( <" A "> e. { w | ( w e. Word S /\ A. k e. ( 0 ..^ ( ( # ` w ) - 1 ) ) ( w ` k ) < ( w ` ( k + 1 ) ) ) } <-> A. w ( w = <" A "> -> ( w e. Word S /\ A. k e. ( 0 ..^ ( ( # ` w ) - 1 ) ) ( w ` k ) < ( w ` ( k + 1 ) ) ) ) ) | 
						
							| 5 |  | eleq1a |  |-  ( <" A "> e. Word S -> ( w = <" A "> -> w e. Word S ) ) | 
						
							| 6 | 1 2 5 | mp2b |  |-  ( w = <" A "> -> w e. Word S ) | 
						
							| 7 |  | fveq2 |  |-  ( w = <" A "> -> ( # ` w ) = ( # ` <" A "> ) ) | 
						
							| 8 | 7 | oveq1d |  |-  ( w = <" A "> -> ( ( # ` w ) - 1 ) = ( ( # ` <" A "> ) - 1 ) ) | 
						
							| 9 |  | s1len |  |-  ( # ` <" A "> ) = 1 | 
						
							| 10 | 9 | oveq1i |  |-  ( ( # ` <" A "> ) - 1 ) = ( 1 - 1 ) | 
						
							| 11 |  | 1m1e0 |  |-  ( 1 - 1 ) = 0 | 
						
							| 12 | 10 11 | eqtri |  |-  ( ( # ` <" A "> ) - 1 ) = 0 | 
						
							| 13 | 8 12 | eqtrdi |  |-  ( w = <" A "> -> ( ( # ` w ) - 1 ) = 0 ) | 
						
							| 14 | 13 | oveq2d |  |-  ( w = <" A "> -> ( 0 ..^ ( ( # ` w ) - 1 ) ) = ( 0 ..^ 0 ) ) | 
						
							| 15 |  | fzo0 |  |-  ( 0 ..^ 0 ) = (/) | 
						
							| 16 | 14 15 | eqtrdi |  |-  ( w = <" A "> -> ( 0 ..^ ( ( # ` w ) - 1 ) ) = (/) ) | 
						
							| 17 |  | rzal |  |-  ( ( 0 ..^ ( ( # ` w ) - 1 ) ) = (/) -> A. k e. ( 0 ..^ ( ( # ` w ) - 1 ) ) ( w ` k ) < ( w ` ( k + 1 ) ) ) | 
						
							| 18 | 16 17 | syl |  |-  ( w = <" A "> -> A. k e. ( 0 ..^ ( ( # ` w ) - 1 ) ) ( w ` k ) < ( w ` ( k + 1 ) ) ) | 
						
							| 19 | 6 18 | jca |  |-  ( w = <" A "> -> ( w e. Word S /\ A. k e. ( 0 ..^ ( ( # ` w ) - 1 ) ) ( w ` k ) < ( w ` ( k + 1 ) ) ) ) | 
						
							| 20 | 4 19 | mpgbir |  |-  <" A "> e. { w | ( w e. Word S /\ A. k e. ( 0 ..^ ( ( # ` w ) - 1 ) ) ( w ` k ) < ( w ` ( k + 1 ) ) ) } | 
						
							| 21 |  | df-upword |  |-  UpWord S = { w | ( w e. Word S /\ A. k e. ( 0 ..^ ( ( # ` w ) - 1 ) ) ( w ` k ) < ( w ` ( k + 1 ) ) ) } | 
						
							| 22 | 20 21 | eleqtrri |  |-  <" A "> e. UpWord S |