| Step | Hyp | Ref | Expression | 
						
							| 1 |  | osumcllem.l | ⊢  ≤   =  ( le ‘ 𝐾 ) | 
						
							| 2 |  | osumcllem.j | ⊢  ∨   =  ( join ‘ 𝐾 ) | 
						
							| 3 |  | osumcllem.a | ⊢ 𝐴  =  ( Atoms ‘ 𝐾 ) | 
						
							| 4 |  | osumcllem.p | ⊢  +   =  ( +𝑃 ‘ 𝐾 ) | 
						
							| 5 |  | osumcllem.o | ⊢  ⊥   =  ( ⊥𝑃 ‘ 𝐾 ) | 
						
							| 6 |  | osumcllem.c | ⊢ 𝐶  =  ( PSubCl ‘ 𝐾 ) | 
						
							| 7 |  | osumcllem.m | ⊢ 𝑀  =  ( 𝑋  +  { 𝑝 } ) | 
						
							| 8 |  | osumcllem.u | ⊢ 𝑈  =  (  ⊥  ‘ (  ⊥  ‘ ( 𝑋  +  𝑌 ) ) ) | 
						
							| 9 |  | n0 | ⊢ ( ( 𝑌  ∩  𝑀 )  ≠  ∅  ↔  ∃ 𝑞 𝑞  ∈  ( 𝑌  ∩  𝑀 ) ) | 
						
							| 10 | 1 2 3 4 5 6 7 8 | osumcllem7N | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  ( 𝑋  ⊆  (  ⊥  ‘ 𝑌 )  ∧  𝑋  ≠  ∅  ∧  𝑝  ∈  𝐴 )  ∧  𝑞  ∈  ( 𝑌  ∩  𝑀 ) )  →  𝑝  ∈  ( 𝑋  +  𝑌 ) ) | 
						
							| 11 | 10 | 3expia | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  ( 𝑋  ⊆  (  ⊥  ‘ 𝑌 )  ∧  𝑋  ≠  ∅  ∧  𝑝  ∈  𝐴 ) )  →  ( 𝑞  ∈  ( 𝑌  ∩  𝑀 )  →  𝑝  ∈  ( 𝑋  +  𝑌 ) ) ) | 
						
							| 12 | 11 | exlimdv | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  ( 𝑋  ⊆  (  ⊥  ‘ 𝑌 )  ∧  𝑋  ≠  ∅  ∧  𝑝  ∈  𝐴 ) )  →  ( ∃ 𝑞 𝑞  ∈  ( 𝑌  ∩  𝑀 )  →  𝑝  ∈  ( 𝑋  +  𝑌 ) ) ) | 
						
							| 13 | 9 12 | biimtrid | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  ( 𝑋  ⊆  (  ⊥  ‘ 𝑌 )  ∧  𝑋  ≠  ∅  ∧  𝑝  ∈  𝐴 ) )  →  ( ( 𝑌  ∩  𝑀 )  ≠  ∅  →  𝑝  ∈  ( 𝑋  +  𝑌 ) ) ) | 
						
							| 14 | 13 | necon1bd | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  ( 𝑋  ⊆  (  ⊥  ‘ 𝑌 )  ∧  𝑋  ≠  ∅  ∧  𝑝  ∈  𝐴 ) )  →  ( ¬  𝑝  ∈  ( 𝑋  +  𝑌 )  →  ( 𝑌  ∩  𝑀 )  =  ∅ ) ) | 
						
							| 15 | 14 | 3impia | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  ( 𝑋  ⊆  (  ⊥  ‘ 𝑌 )  ∧  𝑋  ≠  ∅  ∧  𝑝  ∈  𝐴 )  ∧  ¬  𝑝  ∈  ( 𝑋  +  𝑌 ) )  →  ( 𝑌  ∩  𝑀 )  =  ∅ ) |