| 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 |  | simpl1 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝑈 )  →  𝐾  ∈  HL ) | 
						
							| 10 |  | simpl2 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝑈 )  →  𝑋  ⊆  𝐴 ) | 
						
							| 11 |  | simpr | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝑈 )  →  𝑝  ∈  𝑈 ) | 
						
							| 12 | 11 | snssd | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝑈 )  →  { 𝑝 }  ⊆  𝑈 ) | 
						
							| 13 | 3 4 | paddssat | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  →  ( 𝑋  +  𝑌 )  ⊆  𝐴 ) | 
						
							| 14 | 13 | adantr | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝑈 )  →  ( 𝑋  +  𝑌 )  ⊆  𝐴 ) | 
						
							| 15 | 3 5 | polssatN | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑋  +  𝑌 )  ⊆  𝐴 )  →  (  ⊥  ‘ ( 𝑋  +  𝑌 ) )  ⊆  𝐴 ) | 
						
							| 16 | 9 14 15 | syl2anc | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝑈 )  →  (  ⊥  ‘ ( 𝑋  +  𝑌 ) )  ⊆  𝐴 ) | 
						
							| 17 | 3 5 | polssatN | ⊢ ( ( 𝐾  ∈  HL  ∧  (  ⊥  ‘ ( 𝑋  +  𝑌 ) )  ⊆  𝐴 )  →  (  ⊥  ‘ (  ⊥  ‘ ( 𝑋  +  𝑌 ) ) )  ⊆  𝐴 ) | 
						
							| 18 | 9 16 17 | syl2anc | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝑈 )  →  (  ⊥  ‘ (  ⊥  ‘ ( 𝑋  +  𝑌 ) ) )  ⊆  𝐴 ) | 
						
							| 19 | 8 18 | eqsstrid | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝑈 )  →  𝑈  ⊆  𝐴 ) | 
						
							| 20 | 12 19 | sstrd | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝑈 )  →  { 𝑝 }  ⊆  𝐴 ) | 
						
							| 21 | 3 4 | sspadd1 | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  { 𝑝 }  ⊆  𝐴 )  →  𝑋  ⊆  ( 𝑋  +  { 𝑝 } ) ) | 
						
							| 22 | 9 10 20 21 | syl3anc | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝑈 )  →  𝑋  ⊆  ( 𝑋  +  { 𝑝 } ) ) | 
						
							| 23 | 22 7 | sseqtrrdi | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝑈 )  →  𝑋  ⊆  𝑀 ) | 
						
							| 24 | 1 2 3 4 5 6 7 8 | osumcllem1N | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝑈 )  →  ( 𝑈  ∩  𝑀 )  =  𝑀 ) | 
						
							| 25 | 23 24 | sseqtrrd | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  ∧  𝑝  ∈  𝑈 )  →  𝑋  ⊆  ( 𝑈  ∩  𝑀 ) ) |