| Step | Hyp | Ref | Expression | 
						
							| 1 |  | osum.1 | ⊢ 𝐴  ∈   Cℋ | 
						
							| 2 |  | osum.2 | ⊢ 𝐵  ∈   Cℋ | 
						
							| 3 | 1 2 | cmcm2i | ⊢ ( 𝐴  𝐶ℋ  𝐵  ↔  𝐴  𝐶ℋ  ( ⊥ ‘ 𝐵 ) ) | 
						
							| 4 | 2 | choccli | ⊢ ( ⊥ ‘ 𝐵 )  ∈   Cℋ | 
						
							| 5 | 1 4 | cmbr4i | ⊢ ( 𝐴  𝐶ℋ  ( ⊥ ‘ 𝐵 )  ↔  ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  ⊆  ( ⊥ ‘ 𝐵 ) ) | 
						
							| 6 | 3 5 | bitri | ⊢ ( 𝐴  𝐶ℋ  𝐵  ↔  ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  ⊆  ( ⊥ ‘ 𝐵 ) ) | 
						
							| 7 | 1 | choccli | ⊢ ( ⊥ ‘ 𝐴 )  ∈   Cℋ | 
						
							| 8 | 7 4 | chjcli | ⊢ ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) )  ∈   Cℋ | 
						
							| 9 | 1 8 | chincli | ⊢ ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  ∈   Cℋ | 
						
							| 10 | 9 2 | osumi | ⊢ ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  ⊆  ( ⊥ ‘ 𝐵 )  →  ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  +ℋ  𝐵 )  =  ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  ∨ℋ  𝐵 ) ) | 
						
							| 11 | 7 4 | chjcomi | ⊢ ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) )  =  ( ( ⊥ ‘ 𝐵 )  ∨ℋ  ( ⊥ ‘ 𝐴 ) ) | 
						
							| 12 | 11 | ineq2i | ⊢ ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  =  ( 𝐴  ∩  ( ( ⊥ ‘ 𝐵 )  ∨ℋ  ( ⊥ ‘ 𝐴 ) ) ) | 
						
							| 13 | 12 | oveq1i | ⊢ ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  ∨ℋ  𝐵 )  =  ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐵 )  ∨ℋ  ( ⊥ ‘ 𝐴 ) ) )  ∨ℋ  𝐵 ) | 
						
							| 14 | 4 7 | chjcli | ⊢ ( ( ⊥ ‘ 𝐵 )  ∨ℋ  ( ⊥ ‘ 𝐴 ) )  ∈   Cℋ | 
						
							| 15 | 1 14 | chincli | ⊢ ( 𝐴  ∩  ( ( ⊥ ‘ 𝐵 )  ∨ℋ  ( ⊥ ‘ 𝐴 ) ) )  ∈   Cℋ | 
						
							| 16 | 15 2 | chjcomi | ⊢ ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐵 )  ∨ℋ  ( ⊥ ‘ 𝐴 ) ) )  ∨ℋ  𝐵 )  =  ( 𝐵  ∨ℋ  ( 𝐴  ∩  ( ( ⊥ ‘ 𝐵 )  ∨ℋ  ( ⊥ ‘ 𝐴 ) ) ) ) | 
						
							| 17 | 13 16 | eqtri | ⊢ ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  ∨ℋ  𝐵 )  =  ( 𝐵  ∨ℋ  ( 𝐴  ∩  ( ( ⊥ ‘ 𝐵 )  ∨ℋ  ( ⊥ ‘ 𝐴 ) ) ) ) | 
						
							| 18 | 2 1 | pjoml4i | ⊢ ( 𝐵  ∨ℋ  ( 𝐴  ∩  ( ( ⊥ ‘ 𝐵 )  ∨ℋ  ( ⊥ ‘ 𝐴 ) ) ) )  =  ( 𝐵  ∨ℋ  𝐴 ) | 
						
							| 19 | 2 1 | chjcomi | ⊢ ( 𝐵  ∨ℋ  𝐴 )  =  ( 𝐴  ∨ℋ  𝐵 ) | 
						
							| 20 | 18 19 | eqtri | ⊢ ( 𝐵  ∨ℋ  ( 𝐴  ∩  ( ( ⊥ ‘ 𝐵 )  ∨ℋ  ( ⊥ ‘ 𝐴 ) ) ) )  =  ( 𝐴  ∨ℋ  𝐵 ) | 
						
							| 21 | 17 20 | eqtri | ⊢ ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  ∨ℋ  𝐵 )  =  ( 𝐴  ∨ℋ  𝐵 ) | 
						
							| 22 | 21 | eqeq2i | ⊢ ( ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  +ℋ  𝐵 )  =  ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  ∨ℋ  𝐵 )  ↔  ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  +ℋ  𝐵 )  =  ( 𝐴  ∨ℋ  𝐵 ) ) | 
						
							| 23 |  | inss1 | ⊢ ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  ⊆  𝐴 | 
						
							| 24 | 9 | chshii | ⊢ ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  ∈   Sℋ | 
						
							| 25 | 1 | chshii | ⊢ 𝐴  ∈   Sℋ | 
						
							| 26 | 2 | chshii | ⊢ 𝐵  ∈   Sℋ | 
						
							| 27 | 24 25 26 | shlessi | ⊢ ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  ⊆  𝐴  →  ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  +ℋ  𝐵 )  ⊆  ( 𝐴  +ℋ  𝐵 ) ) | 
						
							| 28 | 23 27 | ax-mp | ⊢ ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  +ℋ  𝐵 )  ⊆  ( 𝐴  +ℋ  𝐵 ) | 
						
							| 29 |  | sseq1 | ⊢ ( ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  +ℋ  𝐵 )  =  ( 𝐴  ∨ℋ  𝐵 )  →  ( ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  +ℋ  𝐵 )  ⊆  ( 𝐴  +ℋ  𝐵 )  ↔  ( 𝐴  ∨ℋ  𝐵 )  ⊆  ( 𝐴  +ℋ  𝐵 ) ) ) | 
						
							| 30 | 28 29 | mpbii | ⊢ ( ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  +ℋ  𝐵 )  =  ( 𝐴  ∨ℋ  𝐵 )  →  ( 𝐴  ∨ℋ  𝐵 )  ⊆  ( 𝐴  +ℋ  𝐵 ) ) | 
						
							| 31 | 22 30 | sylbi | ⊢ ( ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  +ℋ  𝐵 )  =  ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  ∨ℋ  𝐵 )  →  ( 𝐴  ∨ℋ  𝐵 )  ⊆  ( 𝐴  +ℋ  𝐵 ) ) | 
						
							| 32 | 10 31 | syl | ⊢ ( ( 𝐴  ∩  ( ( ⊥ ‘ 𝐴 )  ∨ℋ  ( ⊥ ‘ 𝐵 ) ) )  ⊆  ( ⊥ ‘ 𝐵 )  →  ( 𝐴  ∨ℋ  𝐵 )  ⊆  ( 𝐴  +ℋ  𝐵 ) ) | 
						
							| 33 | 6 32 | sylbi | ⊢ ( 𝐴  𝐶ℋ  𝐵  →  ( 𝐴  ∨ℋ  𝐵 )  ⊆  ( 𝐴  +ℋ  𝐵 ) ) | 
						
							| 34 | 1 2 | chsleji | ⊢ ( 𝐴  +ℋ  𝐵 )  ⊆  ( 𝐴  ∨ℋ  𝐵 ) | 
						
							| 35 | 33 34 | jctil | ⊢ ( 𝐴  𝐶ℋ  𝐵  →  ( ( 𝐴  +ℋ  𝐵 )  ⊆  ( 𝐴  ∨ℋ  𝐵 )  ∧  ( 𝐴  ∨ℋ  𝐵 )  ⊆  ( 𝐴  +ℋ  𝐵 ) ) ) | 
						
							| 36 |  | eqss | ⊢ ( ( 𝐴  +ℋ  𝐵 )  =  ( 𝐴  ∨ℋ  𝐵 )  ↔  ( ( 𝐴  +ℋ  𝐵 )  ⊆  ( 𝐴  ∨ℋ  𝐵 )  ∧  ( 𝐴  ∨ℋ  𝐵 )  ⊆  ( 𝐴  +ℋ  𝐵 ) ) ) | 
						
							| 37 | 35 36 | sylibr | ⊢ ( 𝐴  𝐶ℋ  𝐵  →  ( 𝐴  +ℋ  𝐵 )  =  ( 𝐴  ∨ℋ  𝐵 ) ) |