| 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 |  | simp11 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝐴  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌  ∧  𝑝  ≤  ( 𝑟  ∨  𝑞 ) ) )  →  𝐾  ∈  HL ) | 
						
							| 10 | 9 | hllatd | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝐴  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌  ∧  𝑝  ≤  ( 𝑟  ∨  𝑞 ) ) )  →  𝐾  ∈  Lat ) | 
						
							| 11 |  | simp12 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝐴  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌  ∧  𝑝  ≤  ( 𝑟  ∨  𝑞 ) ) )  →  𝑋  ⊆  𝐴 ) | 
						
							| 12 |  | simp13 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝐴  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌  ∧  𝑝  ≤  ( 𝑟  ∨  𝑞 ) ) )  →  𝑌  ⊆  𝐴 ) | 
						
							| 13 |  | simp31 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝐴  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌  ∧  𝑝  ≤  ( 𝑟  ∨  𝑞 ) ) )  →  𝑟  ∈  𝑋 ) | 
						
							| 14 |  | simp32 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝐴  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌  ∧  𝑝  ≤  ( 𝑟  ∨  𝑞 ) ) )  →  𝑞  ∈  𝑌 ) | 
						
							| 15 |  | simp2 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝐴  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌  ∧  𝑝  ≤  ( 𝑟  ∨  𝑞 ) ) )  →  𝑝  ∈  𝐴 ) | 
						
							| 16 |  | simp33 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝐴  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌  ∧  𝑝  ≤  ( 𝑟  ∨  𝑞 ) ) )  →  𝑝  ≤  ( 𝑟  ∨  𝑞 ) ) | 
						
							| 17 | 1 2 3 4 | elpaddri | ⊢ ( ( ( 𝐾  ∈  Lat  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌 )  ∧  ( 𝑝  ∈  𝐴  ∧  𝑝  ≤  ( 𝑟  ∨  𝑞 ) ) )  →  𝑝  ∈  ( 𝑋  +  𝑌 ) ) | 
						
							| 18 | 10 11 12 13 14 15 16 17 | syl322anc | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝐴  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌  ∧  𝑝  ≤  ( 𝑟  ∨  𝑞 ) ) )  →  𝑝  ∈  ( 𝑋  +  𝑌 ) ) |