| Step | Hyp | Ref | Expression | 
						
							| 1 |  | mdsymlem1.1 | ⊢ 𝐴  ∈   Cℋ | 
						
							| 2 |  | mdsymlem1.2 | ⊢ 𝐵  ∈   Cℋ | 
						
							| 3 |  | mdsymlem1.3 | ⊢ 𝐶  =  ( 𝐴  ∨ℋ  𝑝 ) | 
						
							| 4 |  | chub2 | ⊢ ( ( 𝑝  ∈   Cℋ   ∧  𝐴  ∈   Cℋ  )  →  𝑝  ⊆  ( 𝐴  ∨ℋ  𝑝 ) ) | 
						
							| 5 | 1 4 | mpan2 | ⊢ ( 𝑝  ∈   Cℋ   →  𝑝  ⊆  ( 𝐴  ∨ℋ  𝑝 ) ) | 
						
							| 6 | 5 3 | sseqtrrdi | ⊢ ( 𝑝  ∈   Cℋ   →  𝑝  ⊆  𝐶 ) | 
						
							| 7 | 1 2 | chjcomi | ⊢ ( 𝐴  ∨ℋ  𝐵 )  =  ( 𝐵  ∨ℋ  𝐴 ) | 
						
							| 8 | 7 | sseq2i | ⊢ ( 𝑝  ⊆  ( 𝐴  ∨ℋ  𝐵 )  ↔  𝑝  ⊆  ( 𝐵  ∨ℋ  𝐴 ) ) | 
						
							| 9 | 8 | biimpi | ⊢ ( 𝑝  ⊆  ( 𝐴  ∨ℋ  𝐵 )  →  𝑝  ⊆  ( 𝐵  ∨ℋ  𝐴 ) ) | 
						
							| 10 | 6 9 | anim12i | ⊢ ( ( 𝑝  ∈   Cℋ   ∧  𝑝  ⊆  ( 𝐴  ∨ℋ  𝐵 ) )  →  ( 𝑝  ⊆  𝐶  ∧  𝑝  ⊆  ( 𝐵  ∨ℋ  𝐴 ) ) ) | 
						
							| 11 |  | ssin | ⊢ ( ( 𝑝  ⊆  𝐶  ∧  𝑝  ⊆  ( 𝐵  ∨ℋ  𝐴 ) )  ↔  𝑝  ⊆  ( 𝐶  ∩  ( 𝐵  ∨ℋ  𝐴 ) ) ) | 
						
							| 12 | 10 11 | sylib | ⊢ ( ( 𝑝  ∈   Cℋ   ∧  𝑝  ⊆  ( 𝐴  ∨ℋ  𝐵 ) )  →  𝑝  ⊆  ( 𝐶  ∩  ( 𝐵  ∨ℋ  𝐴 ) ) ) | 
						
							| 13 | 12 | ad2ant2rl | ⊢ ( ( ( 𝑝  ∈   Cℋ   ∧  ( 𝐵  ∩  𝐶 )  ⊆  𝐴 )  ∧  ( 𝐵  𝑀ℋ*  𝐴  ∧  𝑝  ⊆  ( 𝐴  ∨ℋ  𝐵 ) ) )  →  𝑝  ⊆  ( 𝐶  ∩  ( 𝐵  ∨ℋ  𝐴 ) ) ) | 
						
							| 14 |  | chjcl | ⊢ ( ( 𝐴  ∈   Cℋ   ∧  𝑝  ∈   Cℋ  )  →  ( 𝐴  ∨ℋ  𝑝 )  ∈   Cℋ  ) | 
						
							| 15 | 1 14 | mpan | ⊢ ( 𝑝  ∈   Cℋ   →  ( 𝐴  ∨ℋ  𝑝 )  ∈   Cℋ  ) | 
						
							| 16 | 3 15 | eqeltrid | ⊢ ( 𝑝  ∈   Cℋ   →  𝐶  ∈   Cℋ  ) | 
						
							| 17 | 16 | adantr | ⊢ ( ( 𝑝  ∈   Cℋ   ∧  𝐵  𝑀ℋ*  𝐴 )  →  𝐶  ∈   Cℋ  ) | 
						
							| 18 |  | chub1 | ⊢ ( ( 𝐴  ∈   Cℋ   ∧  𝑝  ∈   Cℋ  )  →  𝐴  ⊆  ( 𝐴  ∨ℋ  𝑝 ) ) | 
						
							| 19 | 1 18 | mpan | ⊢ ( 𝑝  ∈   Cℋ   →  𝐴  ⊆  ( 𝐴  ∨ℋ  𝑝 ) ) | 
						
							| 20 | 19 3 | sseqtrrdi | ⊢ ( 𝑝  ∈   Cℋ   →  𝐴  ⊆  𝐶 ) | 
						
							| 21 | 20 | anim2i | ⊢ ( ( 𝐵  𝑀ℋ*  𝐴  ∧  𝑝  ∈   Cℋ  )  →  ( 𝐵  𝑀ℋ*  𝐴  ∧  𝐴  ⊆  𝐶 ) ) | 
						
							| 22 | 21 | ancoms | ⊢ ( ( 𝑝  ∈   Cℋ   ∧  𝐵  𝑀ℋ*  𝐴 )  →  ( 𝐵  𝑀ℋ*  𝐴  ∧  𝐴  ⊆  𝐶 ) ) | 
						
							| 23 |  | dmdi | ⊢ ( ( ( 𝐵  ∈   Cℋ   ∧  𝐴  ∈   Cℋ   ∧  𝐶  ∈   Cℋ  )  ∧  ( 𝐵  𝑀ℋ*  𝐴  ∧  𝐴  ⊆  𝐶 ) )  →  ( ( 𝐶  ∩  𝐵 )  ∨ℋ  𝐴 )  =  ( 𝐶  ∩  ( 𝐵  ∨ℋ  𝐴 ) ) ) | 
						
							| 24 | 2 23 | mp3anl1 | ⊢ ( ( ( 𝐴  ∈   Cℋ   ∧  𝐶  ∈   Cℋ  )  ∧  ( 𝐵  𝑀ℋ*  𝐴  ∧  𝐴  ⊆  𝐶 ) )  →  ( ( 𝐶  ∩  𝐵 )  ∨ℋ  𝐴 )  =  ( 𝐶  ∩  ( 𝐵  ∨ℋ  𝐴 ) ) ) | 
						
							| 25 | 1 24 | mpanl1 | ⊢ ( ( 𝐶  ∈   Cℋ   ∧  ( 𝐵  𝑀ℋ*  𝐴  ∧  𝐴  ⊆  𝐶 ) )  →  ( ( 𝐶  ∩  𝐵 )  ∨ℋ  𝐴 )  =  ( 𝐶  ∩  ( 𝐵  ∨ℋ  𝐴 ) ) ) | 
						
							| 26 | 17 22 25 | syl2anc | ⊢ ( ( 𝑝  ∈   Cℋ   ∧  𝐵  𝑀ℋ*  𝐴 )  →  ( ( 𝐶  ∩  𝐵 )  ∨ℋ  𝐴 )  =  ( 𝐶  ∩  ( 𝐵  ∨ℋ  𝐴 ) ) ) | 
						
							| 27 | 26 | adantlr | ⊢ ( ( ( 𝑝  ∈   Cℋ   ∧  ( 𝐵  ∩  𝐶 )  ⊆  𝐴 )  ∧  𝐵  𝑀ℋ*  𝐴 )  →  ( ( 𝐶  ∩  𝐵 )  ∨ℋ  𝐴 )  =  ( 𝐶  ∩  ( 𝐵  ∨ℋ  𝐴 ) ) ) | 
						
							| 28 |  | incom | ⊢ ( 𝐶  ∩  𝐵 )  =  ( 𝐵  ∩  𝐶 ) | 
						
							| 29 | 28 | oveq1i | ⊢ ( ( 𝐶  ∩  𝐵 )  ∨ℋ  𝐴 )  =  ( ( 𝐵  ∩  𝐶 )  ∨ℋ  𝐴 ) | 
						
							| 30 |  | chincl | ⊢ ( ( 𝐵  ∈   Cℋ   ∧  𝐶  ∈   Cℋ  )  →  ( 𝐵  ∩  𝐶 )  ∈   Cℋ  ) | 
						
							| 31 | 2 30 | mpan | ⊢ ( 𝐶  ∈   Cℋ   →  ( 𝐵  ∩  𝐶 )  ∈   Cℋ  ) | 
						
							| 32 |  | chlejb1 | ⊢ ( ( ( 𝐵  ∩  𝐶 )  ∈   Cℋ   ∧  𝐴  ∈   Cℋ  )  →  ( ( 𝐵  ∩  𝐶 )  ⊆  𝐴  ↔  ( ( 𝐵  ∩  𝐶 )  ∨ℋ  𝐴 )  =  𝐴 ) ) | 
						
							| 33 | 1 32 | mpan2 | ⊢ ( ( 𝐵  ∩  𝐶 )  ∈   Cℋ   →  ( ( 𝐵  ∩  𝐶 )  ⊆  𝐴  ↔  ( ( 𝐵  ∩  𝐶 )  ∨ℋ  𝐴 )  =  𝐴 ) ) | 
						
							| 34 | 16 31 33 | 3syl | ⊢ ( 𝑝  ∈   Cℋ   →  ( ( 𝐵  ∩  𝐶 )  ⊆  𝐴  ↔  ( ( 𝐵  ∩  𝐶 )  ∨ℋ  𝐴 )  =  𝐴 ) ) | 
						
							| 35 | 34 | biimpa | ⊢ ( ( 𝑝  ∈   Cℋ   ∧  ( 𝐵  ∩  𝐶 )  ⊆  𝐴 )  →  ( ( 𝐵  ∩  𝐶 )  ∨ℋ  𝐴 )  =  𝐴 ) | 
						
							| 36 | 29 35 | eqtrid | ⊢ ( ( 𝑝  ∈   Cℋ   ∧  ( 𝐵  ∩  𝐶 )  ⊆  𝐴 )  →  ( ( 𝐶  ∩  𝐵 )  ∨ℋ  𝐴 )  =  𝐴 ) | 
						
							| 37 | 36 | adantr | ⊢ ( ( ( 𝑝  ∈   Cℋ   ∧  ( 𝐵  ∩  𝐶 )  ⊆  𝐴 )  ∧  𝐵  𝑀ℋ*  𝐴 )  →  ( ( 𝐶  ∩  𝐵 )  ∨ℋ  𝐴 )  =  𝐴 ) | 
						
							| 38 | 27 37 | eqtr3d | ⊢ ( ( ( 𝑝  ∈   Cℋ   ∧  ( 𝐵  ∩  𝐶 )  ⊆  𝐴 )  ∧  𝐵  𝑀ℋ*  𝐴 )  →  ( 𝐶  ∩  ( 𝐵  ∨ℋ  𝐴 ) )  =  𝐴 ) | 
						
							| 39 | 38 | adantrr | ⊢ ( ( ( 𝑝  ∈   Cℋ   ∧  ( 𝐵  ∩  𝐶 )  ⊆  𝐴 )  ∧  ( 𝐵  𝑀ℋ*  𝐴  ∧  𝑝  ⊆  ( 𝐴  ∨ℋ  𝐵 ) ) )  →  ( 𝐶  ∩  ( 𝐵  ∨ℋ  𝐴 ) )  =  𝐴 ) | 
						
							| 40 | 13 39 | sseqtrd | ⊢ ( ( ( 𝑝  ∈   Cℋ   ∧  ( 𝐵  ∩  𝐶 )  ⊆  𝐴 )  ∧  ( 𝐵  𝑀ℋ*  𝐴  ∧  𝑝  ⊆  ( 𝐴  ∨ℋ  𝐵 ) ) )  →  𝑝  ⊆  𝐴 ) |