| Step | Hyp | Ref | Expression | 
						
							| 1 |  | dvrdir.b |  | 
						
							| 2 |  | dvrdir.u |  | 
						
							| 3 |  | dvrdir.p |  | 
						
							| 4 |  | dvrdir.t |  | 
						
							| 5 |  | simpl |  | 
						
							| 6 |  | simpr1 |  | 
						
							| 7 |  | simpr2 |  | 
						
							| 8 | 1 2 | unitss |  | 
						
							| 9 |  | simpr3 |  | 
						
							| 10 |  | eqid |  | 
						
							| 11 | 2 10 | unitinvcl |  | 
						
							| 12 | 9 11 | syldan |  | 
						
							| 13 | 8 12 | sselid |  | 
						
							| 14 |  | eqid |  | 
						
							| 15 | 1 3 14 | ringdir |  | 
						
							| 16 | 5 6 7 13 15 | syl13anc |  | 
						
							| 17 |  | ringgrp |  | 
						
							| 18 | 17 | adantr |  | 
						
							| 19 | 1 3 | grpcl |  | 
						
							| 20 | 18 6 7 19 | syl3anc |  | 
						
							| 21 | 1 14 2 10 4 | dvrval |  | 
						
							| 22 | 20 9 21 | syl2anc |  | 
						
							| 23 | 1 14 2 10 4 | dvrval |  | 
						
							| 24 | 6 9 23 | syl2anc |  | 
						
							| 25 | 1 14 2 10 4 | dvrval |  | 
						
							| 26 | 7 9 25 | syl2anc |  | 
						
							| 27 | 24 26 | oveq12d |  | 
						
							| 28 | 16 22 27 | 3eqtr4d |  |