| Step | Hyp | Ref | Expression | 
						
							| 1 |  | islpln2a.l | ⊢  ≤   =  ( le ‘ 𝐾 ) | 
						
							| 2 |  | islpln2a.j | ⊢  ∨   =  ( join ‘ 𝐾 ) | 
						
							| 3 |  | islpln2a.a | ⊢ 𝐴  =  ( Atoms ‘ 𝐾 ) | 
						
							| 4 |  | islpln2a.p | ⊢ 𝑃  =  ( LPlanes ‘ 𝐾 ) | 
						
							| 5 |  | oveq1 | ⊢ ( 𝑄  =  𝑅  →  ( 𝑄  ∨  𝑅 )  =  ( 𝑅  ∨  𝑅 ) ) | 
						
							| 6 | 2 3 | hlatjidm | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑅  ∈  𝐴 )  →  ( 𝑅  ∨  𝑅 )  =  𝑅 ) | 
						
							| 7 | 6 | 3ad2antr2 | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( 𝑅  ∨  𝑅 )  =  𝑅 ) | 
						
							| 8 | 5 7 | sylan9eqr | ⊢ ( ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  ∧  𝑄  =  𝑅 )  →  ( 𝑄  ∨  𝑅 )  =  𝑅 ) | 
						
							| 9 | 8 | oveq1d | ⊢ ( ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  ∧  𝑄  =  𝑅 )  →  ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  =  ( 𝑅  ∨  𝑆 ) ) | 
						
							| 10 |  | simpll | ⊢ ( ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  ∧  𝑄  =  𝑅 )  →  𝐾  ∈  HL ) | 
						
							| 11 |  | simplr2 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  ∧  𝑄  =  𝑅 )  →  𝑅  ∈  𝐴 ) | 
						
							| 12 |  | simplr3 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  ∧  𝑄  =  𝑅 )  →  𝑆  ∈  𝐴 ) | 
						
							| 13 | 2 3 4 | 2atnelpln | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 )  →  ¬  ( 𝑅  ∨  𝑆 )  ∈  𝑃 ) | 
						
							| 14 | 10 11 12 13 | syl3anc | ⊢ ( ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  ∧  𝑄  =  𝑅 )  →  ¬  ( 𝑅  ∨  𝑆 )  ∈  𝑃 ) | 
						
							| 15 | 9 14 | eqneltrd | ⊢ ( ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  ∧  𝑄  =  𝑅 )  →  ¬  ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  ∈  𝑃 ) | 
						
							| 16 | 15 | ex | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( 𝑄  =  𝑅  →  ¬  ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  ∈  𝑃 ) ) | 
						
							| 17 | 16 | necon2ad | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  ∈  𝑃  →  𝑄  ≠  𝑅 ) ) | 
						
							| 18 |  | hllat | ⊢ ( 𝐾  ∈  HL  →  𝐾  ∈  Lat ) | 
						
							| 19 | 18 | adantr | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  𝐾  ∈  Lat ) | 
						
							| 20 |  | simpr3 | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  𝑆  ∈  𝐴 ) | 
						
							| 21 |  | eqid | ⊢ ( Base ‘ 𝐾 )  =  ( Base ‘ 𝐾 ) | 
						
							| 22 | 21 3 | atbase | ⊢ ( 𝑆  ∈  𝐴  →  𝑆  ∈  ( Base ‘ 𝐾 ) ) | 
						
							| 23 | 20 22 | syl | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  𝑆  ∈  ( Base ‘ 𝐾 ) ) | 
						
							| 24 | 21 2 3 | hlatjcl | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴 )  →  ( 𝑄  ∨  𝑅 )  ∈  ( Base ‘ 𝐾 ) ) | 
						
							| 25 | 24 | 3adant3r3 | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( 𝑄  ∨  𝑅 )  ∈  ( Base ‘ 𝐾 ) ) | 
						
							| 26 | 21 1 2 | latleeqj2 | ⊢ ( ( 𝐾  ∈  Lat  ∧  𝑆  ∈  ( Base ‘ 𝐾 )  ∧  ( 𝑄  ∨  𝑅 )  ∈  ( Base ‘ 𝐾 ) )  →  ( 𝑆  ≤  ( 𝑄  ∨  𝑅 )  ↔  ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  =  ( 𝑄  ∨  𝑅 ) ) ) | 
						
							| 27 | 19 23 25 26 | syl3anc | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( 𝑆  ≤  ( 𝑄  ∨  𝑅 )  ↔  ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  =  ( 𝑄  ∨  𝑅 ) ) ) | 
						
							| 28 | 2 3 4 | 2atnelpln | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴 )  →  ¬  ( 𝑄  ∨  𝑅 )  ∈  𝑃 ) | 
						
							| 29 | 28 | 3adant3r3 | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ¬  ( 𝑄  ∨  𝑅 )  ∈  𝑃 ) | 
						
							| 30 |  | eleq1 | ⊢ ( ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  =  ( 𝑄  ∨  𝑅 )  →  ( ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  ∈  𝑃  ↔  ( 𝑄  ∨  𝑅 )  ∈  𝑃 ) ) | 
						
							| 31 | 30 | notbid | ⊢ ( ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  =  ( 𝑄  ∨  𝑅 )  →  ( ¬  ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  ∈  𝑃  ↔  ¬  ( 𝑄  ∨  𝑅 )  ∈  𝑃 ) ) | 
						
							| 32 | 29 31 | syl5ibrcom | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  =  ( 𝑄  ∨  𝑅 )  →  ¬  ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  ∈  𝑃 ) ) | 
						
							| 33 | 27 32 | sylbid | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( 𝑆  ≤  ( 𝑄  ∨  𝑅 )  →  ¬  ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  ∈  𝑃 ) ) | 
						
							| 34 | 33 | con2d | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  ∈  𝑃  →  ¬  𝑆  ≤  ( 𝑄  ∨  𝑅 ) ) ) | 
						
							| 35 | 17 34 | jcad | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  ∈  𝑃  →  ( 𝑄  ≠  𝑅  ∧  ¬  𝑆  ≤  ( 𝑄  ∨  𝑅 ) ) ) ) | 
						
							| 36 | 1 2 3 4 | lplni2 | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 )  ∧  ( 𝑄  ≠  𝑅  ∧  ¬  𝑆  ≤  ( 𝑄  ∨  𝑅 ) ) )  →  ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  ∈  𝑃 ) | 
						
							| 37 | 36 | 3expia | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( ( 𝑄  ≠  𝑅  ∧  ¬  𝑆  ≤  ( 𝑄  ∨  𝑅 ) )  →  ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  ∈  𝑃 ) ) | 
						
							| 38 | 35 37 | impbid | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 )  ∈  𝑃  ↔  ( 𝑄  ≠  𝑅  ∧  ¬  𝑆  ≤  ( 𝑄  ∨  𝑅 ) ) ) ) |