| Step | Hyp | Ref | Expression | 
						
							| 1 |  | normlem8.1 |  | 
						
							| 2 |  | normlem8.2 |  | 
						
							| 3 |  | normlem8.3 |  | 
						
							| 4 |  | normlem8.4 |  | 
						
							| 5 |  | his7 |  | 
						
							| 6 | 1 3 4 5 | mp3an |  | 
						
							| 7 |  | his7 |  | 
						
							| 8 | 2 3 4 7 | mp3an |  | 
						
							| 9 | 6 8 | oveq12i |  | 
						
							| 10 | 3 4 | hvaddcli |  | 
						
							| 11 |  | ax-his2 |  | 
						
							| 12 | 1 2 10 11 | mp3an |  | 
						
							| 13 | 1 3 | hicli |  | 
						
							| 14 | 2 4 | hicli |  | 
						
							| 15 | 1 4 | hicli |  | 
						
							| 16 | 2 3 | hicli |  | 
						
							| 17 | 13 14 15 16 | add42i |  | 
						
							| 18 | 9 12 17 | 3eqtr4i |  |