| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							mdslle1.1 | 
							⊢ 𝐴  ∈   Cℋ   | 
						
						
							| 2 | 
							
								
							 | 
							mdslle1.2 | 
							⊢ 𝐵  ∈   Cℋ   | 
						
						
							| 3 | 
							
								
							 | 
							mdslle1.3 | 
							⊢ 𝐶  ∈   Cℋ   | 
						
						
							| 4 | 
							
								
							 | 
							mdslle1.4 | 
							⊢ 𝐷  ∈   Cℋ   | 
						
						
							| 5 | 
							
								
							 | 
							ssrin | 
							⊢ ( 𝐶  ⊆  𝐷  →  ( 𝐶  ∩  𝐵 )  ⊆  ( 𝐷  ∩  𝐵 ) )  | 
						
						
							| 6 | 
							
								3 2
							 | 
							chincli | 
							⊢ ( 𝐶  ∩  𝐵 )  ∈   Cℋ   | 
						
						
							| 7 | 
							
								4 2
							 | 
							chincli | 
							⊢ ( 𝐷  ∩  𝐵 )  ∈   Cℋ   | 
						
						
							| 8 | 
							
								6 7 1
							 | 
							chlej1i | 
							⊢ ( ( 𝐶  ∩  𝐵 )  ⊆  ( 𝐷  ∩  𝐵 )  →  ( ( 𝐶  ∩  𝐵 )  ∨ℋ  𝐴 )  ⊆  ( ( 𝐷  ∩  𝐵 )  ∨ℋ  𝐴 ) )  | 
						
						
							| 9 | 
							
								
							 | 
							id | 
							⊢ ( 𝐵  𝑀ℋ*  𝐴  →  𝐵  𝑀ℋ*  𝐴 )  | 
						
						
							| 10 | 
							
								
							 | 
							ssin | 
							⊢ ( ( 𝐴  ⊆  𝐶  ∧  𝐴  ⊆  𝐷 )  ↔  𝐴  ⊆  ( 𝐶  ∩  𝐷 ) )  | 
						
						
							| 11 | 
							
								10
							 | 
							bicomi | 
							⊢ ( 𝐴  ⊆  ( 𝐶  ∩  𝐷 )  ↔  ( 𝐴  ⊆  𝐶  ∧  𝐴  ⊆  𝐷 ) )  | 
						
						
							| 12 | 
							
								11
							 | 
							simplbi | 
							⊢ ( 𝐴  ⊆  ( 𝐶  ∩  𝐷 )  →  𝐴  ⊆  𝐶 )  | 
						
						
							| 13 | 
							
								1 2
							 | 
							chjcli | 
							⊢ ( 𝐴  ∨ℋ  𝐵 )  ∈   Cℋ   | 
						
						
							| 14 | 
							
								3 4 13
							 | 
							chlubi | 
							⊢ ( ( 𝐶  ⊆  ( 𝐴  ∨ℋ  𝐵 )  ∧  𝐷  ⊆  ( 𝐴  ∨ℋ  𝐵 ) )  ↔  ( 𝐶  ∨ℋ  𝐷 )  ⊆  ( 𝐴  ∨ℋ  𝐵 ) )  | 
						
						
							| 15 | 
							
								14
							 | 
							bicomi | 
							⊢ ( ( 𝐶  ∨ℋ  𝐷 )  ⊆  ( 𝐴  ∨ℋ  𝐵 )  ↔  ( 𝐶  ⊆  ( 𝐴  ∨ℋ  𝐵 )  ∧  𝐷  ⊆  ( 𝐴  ∨ℋ  𝐵 ) ) )  | 
						
						
							| 16 | 
							
								15
							 | 
							simplbi | 
							⊢ ( ( 𝐶  ∨ℋ  𝐷 )  ⊆  ( 𝐴  ∨ℋ  𝐵 )  →  𝐶  ⊆  ( 𝐴  ∨ℋ  𝐵 ) )  | 
						
						
							| 17 | 
							
								1 2 3
							 | 
							3pm3.2i | 
							⊢ ( 𝐴  ∈   Cℋ   ∧  𝐵  ∈   Cℋ   ∧  𝐶  ∈   Cℋ  )  | 
						
						
							| 18 | 
							
								
							 | 
							dmdsl3 | 
							⊢ ( ( ( 𝐴  ∈   Cℋ   ∧  𝐵  ∈   Cℋ   ∧  𝐶  ∈   Cℋ  )  ∧  ( 𝐵  𝑀ℋ*  𝐴  ∧  𝐴  ⊆  𝐶  ∧  𝐶  ⊆  ( 𝐴  ∨ℋ  𝐵 ) ) )  →  ( ( 𝐶  ∩  𝐵 )  ∨ℋ  𝐴 )  =  𝐶 )  | 
						
						
							| 19 | 
							
								17 18
							 | 
							mpan | 
							⊢ ( ( 𝐵  𝑀ℋ*  𝐴  ∧  𝐴  ⊆  𝐶  ∧  𝐶  ⊆  ( 𝐴  ∨ℋ  𝐵 ) )  →  ( ( 𝐶  ∩  𝐵 )  ∨ℋ  𝐴 )  =  𝐶 )  | 
						
						
							| 20 | 
							
								9 12 16 19
							 | 
							syl3an | 
							⊢ ( ( 𝐵  𝑀ℋ*  𝐴  ∧  𝐴  ⊆  ( 𝐶  ∩  𝐷 )  ∧  ( 𝐶  ∨ℋ  𝐷 )  ⊆  ( 𝐴  ∨ℋ  𝐵 ) )  →  ( ( 𝐶  ∩  𝐵 )  ∨ℋ  𝐴 )  =  𝐶 )  | 
						
						
							| 21 | 
							
								11
							 | 
							simprbi | 
							⊢ ( 𝐴  ⊆  ( 𝐶  ∩  𝐷 )  →  𝐴  ⊆  𝐷 )  | 
						
						
							| 22 | 
							
								15
							 | 
							simprbi | 
							⊢ ( ( 𝐶  ∨ℋ  𝐷 )  ⊆  ( 𝐴  ∨ℋ  𝐵 )  →  𝐷  ⊆  ( 𝐴  ∨ℋ  𝐵 ) )  | 
						
						
							| 23 | 
							
								1 2 4
							 | 
							3pm3.2i | 
							⊢ ( 𝐴  ∈   Cℋ   ∧  𝐵  ∈   Cℋ   ∧  𝐷  ∈   Cℋ  )  | 
						
						
							| 24 | 
							
								
							 | 
							dmdsl3 | 
							⊢ ( ( ( 𝐴  ∈   Cℋ   ∧  𝐵  ∈   Cℋ   ∧  𝐷  ∈   Cℋ  )  ∧  ( 𝐵  𝑀ℋ*  𝐴  ∧  𝐴  ⊆  𝐷  ∧  𝐷  ⊆  ( 𝐴  ∨ℋ  𝐵 ) ) )  →  ( ( 𝐷  ∩  𝐵 )  ∨ℋ  𝐴 )  =  𝐷 )  | 
						
						
							| 25 | 
							
								23 24
							 | 
							mpan | 
							⊢ ( ( 𝐵  𝑀ℋ*  𝐴  ∧  𝐴  ⊆  𝐷  ∧  𝐷  ⊆  ( 𝐴  ∨ℋ  𝐵 ) )  →  ( ( 𝐷  ∩  𝐵 )  ∨ℋ  𝐴 )  =  𝐷 )  | 
						
						
							| 26 | 
							
								9 21 22 25
							 | 
							syl3an | 
							⊢ ( ( 𝐵  𝑀ℋ*  𝐴  ∧  𝐴  ⊆  ( 𝐶  ∩  𝐷 )  ∧  ( 𝐶  ∨ℋ  𝐷 )  ⊆  ( 𝐴  ∨ℋ  𝐵 ) )  →  ( ( 𝐷  ∩  𝐵 )  ∨ℋ  𝐴 )  =  𝐷 )  | 
						
						
							| 27 | 
							
								20 26
							 | 
							sseq12d | 
							⊢ ( ( 𝐵  𝑀ℋ*  𝐴  ∧  𝐴  ⊆  ( 𝐶  ∩  𝐷 )  ∧  ( 𝐶  ∨ℋ  𝐷 )  ⊆  ( 𝐴  ∨ℋ  𝐵 ) )  →  ( ( ( 𝐶  ∩  𝐵 )  ∨ℋ  𝐴 )  ⊆  ( ( 𝐷  ∩  𝐵 )  ∨ℋ  𝐴 )  ↔  𝐶  ⊆  𝐷 ) )  | 
						
						
							| 28 | 
							
								8 27
							 | 
							imbitrid | 
							⊢ ( ( 𝐵  𝑀ℋ*  𝐴  ∧  𝐴  ⊆  ( 𝐶  ∩  𝐷 )  ∧  ( 𝐶  ∨ℋ  𝐷 )  ⊆  ( 𝐴  ∨ℋ  𝐵 ) )  →  ( ( 𝐶  ∩  𝐵 )  ⊆  ( 𝐷  ∩  𝐵 )  →  𝐶  ⊆  𝐷 ) )  | 
						
						
							| 29 | 
							
								5 28
							 | 
							impbid2 | 
							⊢ ( ( 𝐵  𝑀ℋ*  𝐴  ∧  𝐴  ⊆  ( 𝐶  ∩  𝐷 )  ∧  ( 𝐶  ∨ℋ  𝐷 )  ⊆  ( 𝐴  ∨ℋ  𝐵 ) )  →  ( 𝐶  ⊆  𝐷  ↔  ( 𝐶  ∩  𝐵 )  ⊆  ( 𝐷  ∩  𝐵 ) ) )  |