| Step | Hyp | Ref | Expression | 
						
							| 1 |  | lautset.b |  | 
						
							| 2 |  | lautset.l |  | 
						
							| 3 |  | lautset.i |  | 
						
							| 4 |  | elex |  | 
						
							| 5 |  | fveq2 |  | 
						
							| 6 | 5 1 | eqtr4di |  | 
						
							| 7 | 6 | f1oeq2d |  | 
						
							| 8 |  | f1oeq3 |  | 
						
							| 9 | 6 8 | syl |  | 
						
							| 10 | 7 9 | bitrd |  | 
						
							| 11 |  | fveq2 |  | 
						
							| 12 | 11 2 | eqtr4di |  | 
						
							| 13 | 12 | breqd |  | 
						
							| 14 | 12 | breqd |  | 
						
							| 15 | 13 14 | bibi12d |  | 
						
							| 16 | 6 15 | raleqbidv |  | 
						
							| 17 | 6 16 | raleqbidv |  | 
						
							| 18 | 10 17 | anbi12d |  | 
						
							| 19 | 18 | abbidv |  | 
						
							| 20 |  | df-laut |  | 
						
							| 21 | 1 | fvexi |  | 
						
							| 22 | 21 21 | mapval |  | 
						
							| 23 |  | ovex |  | 
						
							| 24 | 22 23 | eqeltrri |  | 
						
							| 25 |  | f1of |  | 
						
							| 26 | 25 | ss2abi |  | 
						
							| 27 | 24 26 | ssexi |  | 
						
							| 28 |  | simpl |  | 
						
							| 29 | 28 | ss2abi |  | 
						
							| 30 | 27 29 | ssexi |  | 
						
							| 31 | 19 20 30 | fvmpt |  | 
						
							| 32 | 3 31 | eqtrid |  | 
						
							| 33 | 4 32 | syl |  |