| Step | Hyp | Ref | Expression | 
						
							| 1 |  | simpr |  | 
						
							| 2 |  | cnex |  | 
						
							| 3 |  | ssexg |  | 
						
							| 4 | 1 2 3 | sylancl |  | 
						
							| 5 |  | snex |  | 
						
							| 6 |  | unexg |  | 
						
							| 7 | 4 5 6 | sylancl |  | 
						
							| 8 |  | unss1 |  | 
						
							| 9 | 8 | adantr |  | 
						
							| 10 |  | mapss |  | 
						
							| 11 | 7 9 10 | syl2anc |  | 
						
							| 12 |  | ssrexv |  | 
						
							| 13 | 11 12 | syl |  | 
						
							| 14 | 13 | reximdv |  | 
						
							| 15 | 14 | ss2abdv |  | 
						
							| 16 |  | sstr |  | 
						
							| 17 |  | plyval |  | 
						
							| 18 | 16 17 | syl |  | 
						
							| 19 |  | plyval |  | 
						
							| 20 | 19 | adantl |  | 
						
							| 21 | 15 18 20 | 3sstr4d |  |