| 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 |  | islpln2a.y | ⊢ 𝑌  =  ( ( 𝑄  ∨  𝑅 )  ∨  𝑆 ) | 
						
							| 6 | 1 2 3 | 3noncolr1N | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 )  ∧  ( 𝑄  ≠  𝑅  ∧  ¬  𝑆  ≤  ( 𝑄  ∨  𝑅 ) ) )  →  ( 𝑆  ≠  𝑄  ∧  ¬  𝑅  ≤  ( 𝑆  ∨  𝑄 ) ) ) | 
						
							| 7 | 6 | simprd | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 )  ∧  ( 𝑄  ≠  𝑅  ∧  ¬  𝑆  ≤  ( 𝑄  ∨  𝑅 ) ) )  →  ¬  𝑅  ≤  ( 𝑆  ∨  𝑄 ) ) | 
						
							| 8 | 7 | 3expia | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( ( 𝑄  ≠  𝑅  ∧  ¬  𝑆  ≤  ( 𝑄  ∨  𝑅 ) )  →  ¬  𝑅  ≤  ( 𝑆  ∨  𝑄 ) ) ) | 
						
							| 9 | 1 2 3 4 5 | islpln2ah | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( 𝑌  ∈  𝑃  ↔  ( 𝑄  ≠  𝑅  ∧  ¬  𝑆  ≤  ( 𝑄  ∨  𝑅 ) ) ) ) | 
						
							| 10 | 2 3 | hlatjcom | ⊢ ( ( 𝐾  ∈  HL  ∧  𝑄  ∈  𝐴  ∧  𝑆  ∈  𝐴 )  →  ( 𝑄  ∨  𝑆 )  =  ( 𝑆  ∨  𝑄 ) ) | 
						
							| 11 | 10 | 3adant3r2 | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( 𝑄  ∨  𝑆 )  =  ( 𝑆  ∨  𝑄 ) ) | 
						
							| 12 | 11 | breq2d | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( 𝑅  ≤  ( 𝑄  ∨  𝑆 )  ↔  𝑅  ≤  ( 𝑆  ∨  𝑄 ) ) ) | 
						
							| 13 | 12 | notbid | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( ¬  𝑅  ≤  ( 𝑄  ∨  𝑆 )  ↔  ¬  𝑅  ≤  ( 𝑆  ∨  𝑄 ) ) ) | 
						
							| 14 | 8 9 13 | 3imtr4d | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 ) )  →  ( 𝑌  ∈  𝑃  →  ¬  𝑅  ≤  ( 𝑄  ∨  𝑆 ) ) ) | 
						
							| 15 | 14 | 3impia | ⊢ ( ( 𝐾  ∈  HL  ∧  ( 𝑄  ∈  𝐴  ∧  𝑅  ∈  𝐴  ∧  𝑆  ∈  𝐴 )  ∧  𝑌  ∈  𝑃 )  →  ¬  𝑅  ≤  ( 𝑄  ∨  𝑆 ) ) |