| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							ltrnatb.b | 
							⊢ 𝐵  =  ( Base ‘ 𝐾 )  | 
						
						
							| 2 | 
							
								
							 | 
							ltrnatb.a | 
							⊢ 𝐴  =  ( Atoms ‘ 𝐾 )  | 
						
						
							| 3 | 
							
								
							 | 
							ltrnatb.h | 
							⊢ 𝐻  =  ( LHyp ‘ 𝐾 )  | 
						
						
							| 4 | 
							
								
							 | 
							ltrnatb.t | 
							⊢ 𝑇  =  ( ( LTrn ‘ 𝐾 ) ‘ 𝑊 )  | 
						
						
							| 5 | 
							
								1 3 4
							 | 
							ltrn1o | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  𝐹  ∈  𝑇 )  →  𝐹 : 𝐵 –1-1-onto→ 𝐵 )  | 
						
						
							| 6 | 
							
								
							 | 
							f1ocnvdm | 
							⊢ ( ( 𝐹 : 𝐵 –1-1-onto→ 𝐵  ∧  𝑃  ∈  𝐵 )  →  ( ◡ 𝐹 ‘ 𝑃 )  ∈  𝐵 )  | 
						
						
							| 7 | 
							
								5 6
							 | 
							stoic3 | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  𝐹  ∈  𝑇  ∧  𝑃  ∈  𝐵 )  →  ( ◡ 𝐹 ‘ 𝑃 )  ∈  𝐵 )  | 
						
						
							| 8 | 
							
								1 2 3 4
							 | 
							ltrnatb | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  𝐹  ∈  𝑇  ∧  ( ◡ 𝐹 ‘ 𝑃 )  ∈  𝐵 )  →  ( ( ◡ 𝐹 ‘ 𝑃 )  ∈  𝐴  ↔  ( 𝐹 ‘ ( ◡ 𝐹 ‘ 𝑃 ) )  ∈  𝐴 ) )  | 
						
						
							| 9 | 
							
								7 8
							 | 
							syld3an3 | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  𝐹  ∈  𝑇  ∧  𝑃  ∈  𝐵 )  →  ( ( ◡ 𝐹 ‘ 𝑃 )  ∈  𝐴  ↔  ( 𝐹 ‘ ( ◡ 𝐹 ‘ 𝑃 ) )  ∈  𝐴 ) )  | 
						
						
							| 10 | 
							
								
							 | 
							f1ocnvfv2 | 
							⊢ ( ( 𝐹 : 𝐵 –1-1-onto→ 𝐵  ∧  𝑃  ∈  𝐵 )  →  ( 𝐹 ‘ ( ◡ 𝐹 ‘ 𝑃 ) )  =  𝑃 )  | 
						
						
							| 11 | 
							
								5 10
							 | 
							stoic3 | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  𝐹  ∈  𝑇  ∧  𝑃  ∈  𝐵 )  →  ( 𝐹 ‘ ( ◡ 𝐹 ‘ 𝑃 ) )  =  𝑃 )  | 
						
						
							| 12 | 
							
								11
							 | 
							eleq1d | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  𝐹  ∈  𝑇  ∧  𝑃  ∈  𝐵 )  →  ( ( 𝐹 ‘ ( ◡ 𝐹 ‘ 𝑃 ) )  ∈  𝐴  ↔  𝑃  ∈  𝐴 ) )  | 
						
						
							| 13 | 
							
								9 12
							 | 
							bitr2d | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  𝐹  ∈  𝑇  ∧  𝑃  ∈  𝐵 )  →  ( 𝑃  ∈  𝐴  ↔  ( ◡ 𝐹 ‘ 𝑃 )  ∈  𝐴 ) )  |