| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							ltrnel.l | 
							⊢  ≤   =  ( le ‘ 𝐾 )  | 
						
						
							| 2 | 
							
								
							 | 
							ltrnel.a | 
							⊢ 𝐴  =  ( Atoms ‘ 𝐾 )  | 
						
						
							| 3 | 
							
								
							 | 
							ltrnel.h | 
							⊢ 𝐻  =  ( LHyp ‘ 𝐾 )  | 
						
						
							| 4 | 
							
								
							 | 
							ltrnel.t | 
							⊢ 𝑇  =  ( ( LTrn ‘ 𝐾 ) ‘ 𝑊 )  | 
						
						
							| 5 | 
							
								
							 | 
							simp1 | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝑃  ∈  𝐴 )  →  ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 ) )  | 
						
						
							| 6 | 
							
								
							 | 
							simp2r | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝑃  ∈  𝐴 )  →  𝐺  ∈  𝑇 )  | 
						
						
							| 7 | 
							
								
							 | 
							eqid | 
							⊢ ( Base ‘ 𝐾 )  =  ( Base ‘ 𝐾 )  | 
						
						
							| 8 | 
							
								7 3 4
							 | 
							ltrn1o | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  𝐺  ∈  𝑇 )  →  𝐺 : ( Base ‘ 𝐾 ) –1-1-onto→ ( Base ‘ 𝐾 ) )  | 
						
						
							| 9 | 
							
								5 6 8
							 | 
							syl2anc | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝑃  ∈  𝐴 )  →  𝐺 : ( Base ‘ 𝐾 ) –1-1-onto→ ( Base ‘ 𝐾 ) )  | 
						
						
							| 10 | 
							
								
							 | 
							f1of | 
							⊢ ( 𝐺 : ( Base ‘ 𝐾 ) –1-1-onto→ ( Base ‘ 𝐾 )  →  𝐺 : ( Base ‘ 𝐾 ) ⟶ ( Base ‘ 𝐾 ) )  | 
						
						
							| 11 | 
							
								9 10
							 | 
							syl | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝑃  ∈  𝐴 )  →  𝐺 : ( Base ‘ 𝐾 ) ⟶ ( Base ‘ 𝐾 ) )  | 
						
						
							| 12 | 
							
								7 2
							 | 
							atbase | 
							⊢ ( 𝑃  ∈  𝐴  →  𝑃  ∈  ( Base ‘ 𝐾 ) )  | 
						
						
							| 13 | 
							
								12
							 | 
							3ad2ant3 | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝑃  ∈  𝐴 )  →  𝑃  ∈  ( Base ‘ 𝐾 ) )  | 
						
						
							| 14 | 
							
								
							 | 
							fvco3 | 
							⊢ ( ( 𝐺 : ( Base ‘ 𝐾 ) ⟶ ( Base ‘ 𝐾 )  ∧  𝑃  ∈  ( Base ‘ 𝐾 ) )  →  ( ( 𝐹  ∘  𝐺 ) ‘ 𝑃 )  =  ( 𝐹 ‘ ( 𝐺 ‘ 𝑃 ) ) )  | 
						
						
							| 15 | 
							
								11 13 14
							 | 
							syl2anc | 
							⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝑃  ∈  𝐴 )  →  ( ( 𝐹  ∘  𝐺 ) ‘ 𝑃 )  =  ( 𝐹 ‘ ( 𝐺 ‘ 𝑃 ) ) )  |