| 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 | 
							
								
							 | 
							n0i | 
							⊢ ( 𝑟  ∈  ( 𝑋  ∩  𝑌 )  →  ¬  ( 𝑋  ∩  𝑌 )  =  ∅ )  | 
						
						
							| 10 | 
							
								
							 | 
							incom | 
							⊢ ( 𝑋  ∩  𝑌 )  =  ( 𝑌  ∩  𝑋 )  | 
						
						
							| 11 | 
							
								
							 | 
							sslin | 
							⊢ ( 𝑋  ⊆  (  ⊥  ‘ 𝑌 )  →  ( 𝑌  ∩  𝑋 )  ⊆  ( 𝑌  ∩  (  ⊥  ‘ 𝑌 ) ) )  | 
						
						
							| 12 | 
							
								11
							 | 
							3ad2ant3 | 
							⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  ( 𝑌  ∩  𝑋 )  ⊆  ( 𝑌  ∩  (  ⊥  ‘ 𝑌 ) ) )  | 
						
						
							| 13 | 
							
								10 12
							 | 
							eqsstrid | 
							⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  ( 𝑋  ∩  𝑌 )  ⊆  ( 𝑌  ∩  (  ⊥  ‘ 𝑌 ) ) )  | 
						
						
							| 14 | 
							
								3 5
							 | 
							pnonsingN | 
							⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴 )  →  ( 𝑌  ∩  (  ⊥  ‘ 𝑌 ) )  =  ∅ )  | 
						
						
							| 15 | 
							
								14
							 | 
							3adant3 | 
							⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  ( 𝑌  ∩  (  ⊥  ‘ 𝑌 ) )  =  ∅ )  | 
						
						
							| 16 | 
							
								13 15
							 | 
							sseqtrd | 
							⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  ( 𝑋  ∩  𝑌 )  ⊆  ∅ )  | 
						
						
							| 17 | 
							
								
							 | 
							ss0b | 
							⊢ ( ( 𝑋  ∩  𝑌 )  ⊆  ∅  ↔  ( 𝑋  ∩  𝑌 )  =  ∅ )  | 
						
						
							| 18 | 
							
								16 17
							 | 
							sylib | 
							⊢ ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  →  ( 𝑋  ∩  𝑌 )  =  ∅ )  | 
						
						
							| 19 | 
							
								18
							 | 
							adantr | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌 ) )  →  ( 𝑋  ∩  𝑌 )  =  ∅ )  | 
						
						
							| 20 | 
							
								9 19
							 | 
							nsyl3 | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌 ) )  →  ¬  𝑟  ∈  ( 𝑋  ∩  𝑌 ) )  | 
						
						
							| 21 | 
							
								
							 | 
							simprr | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌 ) )  →  𝑞  ∈  𝑌 )  | 
						
						
							| 22 | 
							
								
							 | 
							eleq1w | 
							⊢ ( 𝑞  =  𝑟  →  ( 𝑞  ∈  𝑌  ↔  𝑟  ∈  𝑌 ) )  | 
						
						
							| 23 | 
							
								21 22
							 | 
							syl5ibcom | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌 ) )  →  ( 𝑞  =  𝑟  →  𝑟  ∈  𝑌 ) )  | 
						
						
							| 24 | 
							
								
							 | 
							simprl | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌 ) )  →  𝑟  ∈  𝑋 )  | 
						
						
							| 25 | 
							
								23 24
							 | 
							jctild | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌 ) )  →  ( 𝑞  =  𝑟  →  ( 𝑟  ∈  𝑋  ∧  𝑟  ∈  𝑌 ) ) )  | 
						
						
							| 26 | 
							
								
							 | 
							elin | 
							⊢ ( 𝑟  ∈  ( 𝑋  ∩  𝑌 )  ↔  ( 𝑟  ∈  𝑋  ∧  𝑟  ∈  𝑌 ) )  | 
						
						
							| 27 | 
							
								25 26
							 | 
							imbitrrdi | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌 ) )  →  ( 𝑞  =  𝑟  →  𝑟  ∈  ( 𝑋  ∩  𝑌 ) ) )  | 
						
						
							| 28 | 
							
								27
							 | 
							necon3bd | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌 ) )  →  ( ¬  𝑟  ∈  ( 𝑋  ∩  𝑌 )  →  𝑞  ≠  𝑟 ) )  | 
						
						
							| 29 | 
							
								20 28
							 | 
							mpd | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑌  ⊆  𝐴  ∧  𝑋  ⊆  (  ⊥  ‘ 𝑌 ) )  ∧  ( 𝑟  ∈  𝑋  ∧  𝑞  ∈  𝑌 ) )  →  𝑞  ≠  𝑟 )  |