| 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 |  | incom | ⊢ ( (  ⊥  ‘ 𝑋 )  ∩  𝑈 )  =  ( 𝑈  ∩  (  ⊥  ‘ 𝑋 ) ) | 
						
							| 10 |  | simp1 | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  𝐾  ∈  HL ) | 
						
							| 11 |  | simp3 | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) ) | 
						
							| 12 | 3 6 | psubclssatN | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶 )  →  𝑌  ⊆  𝐴 ) | 
						
							| 13 | 12 | 3adant3 | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  𝑌  ⊆  𝐴 ) | 
						
							| 14 | 3 5 | polssatN | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴 )  →  (  ⊥  ‘ 𝑌 )  ⊆  𝐴 ) | 
						
							| 15 | 10 13 14 | syl2anc | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  (  ⊥  ‘ 𝑌 )  ⊆  𝐴 ) | 
						
							| 16 | 11 15 | sstrd | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  𝑋  ⊆  𝐴 ) | 
						
							| 17 | 3 4 5 | poldmj1N | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  𝐴 )  →  (  ⊥  ‘ ( 𝑋  +  𝑌 ) )  =  ( (  ⊥  ‘ 𝑋 )  ∩  (  ⊥  ‘ 𝑌 ) ) ) | 
						
							| 18 | 10 16 13 17 | syl3anc | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  (  ⊥  ‘ ( 𝑋  +  𝑌 ) )  =  ( (  ⊥  ‘ 𝑋 )  ∩  (  ⊥  ‘ 𝑌 ) ) ) | 
						
							| 19 |  | incom | ⊢ ( (  ⊥  ‘ 𝑋 )  ∩  (  ⊥  ‘ 𝑌 ) )  =  ( (  ⊥  ‘ 𝑌 )  ∩  (  ⊥  ‘ 𝑋 ) ) | 
						
							| 20 | 18 19 | eqtrdi | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  (  ⊥  ‘ ( 𝑋  +  𝑌 ) )  =  ( (  ⊥  ‘ 𝑌 )  ∩  (  ⊥  ‘ 𝑋 ) ) ) | 
						
							| 21 | 20 | fveq2d | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  (  ⊥  ‘ (  ⊥  ‘ ( 𝑋  +  𝑌 ) ) )  =  (  ⊥  ‘ ( (  ⊥  ‘ 𝑌 )  ∩  (  ⊥  ‘ 𝑋 ) ) ) ) | 
						
							| 22 | 8 21 | eqtrid | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  𝑈  =  (  ⊥  ‘ ( (  ⊥  ‘ 𝑌 )  ∩  (  ⊥  ‘ 𝑋 ) ) ) ) | 
						
							| 23 | 22 | ineq1d | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  ( 𝑈  ∩  (  ⊥  ‘ 𝑋 ) )  =  ( (  ⊥  ‘ ( (  ⊥  ‘ 𝑌 )  ∩  (  ⊥  ‘ 𝑋 ) ) )  ∩  (  ⊥  ‘ 𝑋 ) ) ) | 
						
							| 24 | 3 5 | polcon2N | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  𝑌  ⊆  (  ⊥  ‘ 𝑋 ) ) | 
						
							| 25 | 13 24 | syld3an2 | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  𝑌  ⊆  (  ⊥  ‘ 𝑋 ) ) | 
						
							| 26 | 3 5 | poml5N | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑋  ⊆  𝐴  ∧  𝑌  ⊆  (  ⊥  ‘ 𝑋 ) )  →  ( (  ⊥  ‘ ( (  ⊥  ‘ 𝑌 )  ∩  (  ⊥  ‘ 𝑋 ) ) )  ∩  (  ⊥  ‘ 𝑋 ) )  =  (  ⊥  ‘ (  ⊥  ‘ 𝑌 ) ) ) | 
						
							| 27 | 10 16 25 26 | syl3anc | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  ( (  ⊥  ‘ ( (  ⊥  ‘ 𝑌 )  ∩  (  ⊥  ‘ 𝑋 ) ) )  ∩  (  ⊥  ‘ 𝑋 ) )  =  (  ⊥  ‘ (  ⊥  ‘ 𝑌 ) ) ) | 
						
							| 28 | 5 6 | psubcli2N | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶 )  →  (  ⊥  ‘ (  ⊥  ‘ 𝑌 ) )  =  𝑌 ) | 
						
							| 29 | 28 | 3adant3 | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  (  ⊥  ‘ (  ⊥  ‘ 𝑌 ) )  =  𝑌 ) | 
						
							| 30 | 23 27 29 | 3eqtrd | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  ( 𝑈  ∩  (  ⊥  ‘ 𝑋 ) )  =  𝑌 ) | 
						
							| 31 | 9 30 | eqtrid | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ∈  𝐶  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  ( (  ⊥  ‘ 𝑋 )  ∩  𝑈 )  =  𝑌 ) |