| Step | Hyp | Ref | Expression | 
						
							| 1 |  | cvrletr.b |  | 
						
							| 2 |  | cvrletr.l |  | 
						
							| 3 |  | cvrletr.s |  | 
						
							| 4 |  | cvrletr.c |  | 
						
							| 5 | 1 3 4 | cvrnbtwn |  | 
						
							| 6 | 2 3 | pltval |  | 
						
							| 7 | 6 | 3adant3r2 |  | 
						
							| 8 | 7 | 3adant3 |  | 
						
							| 9 | 8 | anbi1d |  | 
						
							| 10 | 9 | notbid |  | 
						
							| 11 |  | an32 |  | 
						
							| 12 |  | df-ne |  | 
						
							| 13 | 12 | anbi2i |  | 
						
							| 14 | 11 13 | bitri |  | 
						
							| 15 | 14 | notbii |  | 
						
							| 16 |  | iman |  | 
						
							| 17 | 15 16 | bitr4i |  | 
						
							| 18 | 10 17 | bitrdi |  | 
						
							| 19 | 5 18 | mpbid |  | 
						
							| 20 | 1 2 | posref |  | 
						
							| 21 |  | breq2 |  | 
						
							| 22 | 20 21 | syl5ibcom |  | 
						
							| 23 | 22 | 3ad2antr1 |  | 
						
							| 24 | 23 | 3adant3 |  | 
						
							| 25 |  | simp1 |  | 
						
							| 26 |  | simp21 |  | 
						
							| 27 |  | simp22 |  | 
						
							| 28 |  | simp3 |  | 
						
							| 29 | 1 3 4 | cvrlt |  | 
						
							| 30 | 25 26 27 28 29 | syl31anc |  | 
						
							| 31 |  | breq1 |  | 
						
							| 32 | 30 31 | syl5ibcom |  | 
						
							| 33 | 24 32 | jcad |  | 
						
							| 34 | 19 33 | impbid |  |