| Step | Hyp | Ref | Expression | 
						
							| 1 |  | cdlemg46.b | ⊢ 𝐵  =  ( Base ‘ 𝐾 ) | 
						
							| 2 |  | cdlemg46.h | ⊢ 𝐻  =  ( LHyp ‘ 𝐾 ) | 
						
							| 3 |  | cdlemg46.t | ⊢ 𝑇  =  ( ( LTrn ‘ 𝐾 ) ‘ 𝑊 ) | 
						
							| 4 |  | simp1 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝐹  =  (  I   ↾  𝐵 ) )  →  ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 ) ) | 
						
							| 5 |  | simp2r | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝐹  =  (  I   ↾  𝐵 ) )  →  𝐺  ∈  𝑇 ) | 
						
							| 6 | 1 2 3 | ltrn1o | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  𝐺  ∈  𝑇 )  →  𝐺 : 𝐵 –1-1-onto→ 𝐵 ) | 
						
							| 7 | 4 5 6 | syl2anc | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝐹  =  (  I   ↾  𝐵 ) )  →  𝐺 : 𝐵 –1-1-onto→ 𝐵 ) | 
						
							| 8 |  | f1of | ⊢ ( 𝐺 : 𝐵 –1-1-onto→ 𝐵  →  𝐺 : 𝐵 ⟶ 𝐵 ) | 
						
							| 9 | 7 8 | syl | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝐹  =  (  I   ↾  𝐵 ) )  →  𝐺 : 𝐵 ⟶ 𝐵 ) | 
						
							| 10 |  | fcoi1 | ⊢ ( 𝐺 : 𝐵 ⟶ 𝐵  →  ( 𝐺  ∘  (  I   ↾  𝐵 ) )  =  𝐺 ) | 
						
							| 11 | 9 10 | syl | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝐹  =  (  I   ↾  𝐵 ) )  →  ( 𝐺  ∘  (  I   ↾  𝐵 ) )  =  𝐺 ) | 
						
							| 12 |  | simp3 | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝐹  =  (  I   ↾  𝐵 ) )  →  𝐹  =  (  I   ↾  𝐵 ) ) | 
						
							| 13 | 12 | coeq2d | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝐹  =  (  I   ↾  𝐵 ) )  →  ( 𝐺  ∘  𝐹 )  =  ( 𝐺  ∘  (  I   ↾  𝐵 ) ) ) | 
						
							| 14 | 12 | coeq1d | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝐹  =  (  I   ↾  𝐵 ) )  →  ( 𝐹  ∘  𝐺 )  =  ( (  I   ↾  𝐵 )  ∘  𝐺 ) ) | 
						
							| 15 |  | fcoi2 | ⊢ ( 𝐺 : 𝐵 ⟶ 𝐵  →  ( (  I   ↾  𝐵 )  ∘  𝐺 )  =  𝐺 ) | 
						
							| 16 | 9 15 | syl | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝐹  =  (  I   ↾  𝐵 ) )  →  ( (  I   ↾  𝐵 )  ∘  𝐺 )  =  𝐺 ) | 
						
							| 17 | 14 16 | eqtrd | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝐹  =  (  I   ↾  𝐵 ) )  →  ( 𝐹  ∘  𝐺 )  =  𝐺 ) | 
						
							| 18 | 11 13 17 | 3eqtr4rd | ⊢ ( ( ( 𝐾  ∈  HL  ∧  𝑊  ∈  𝐻 )  ∧  ( 𝐹  ∈  𝑇  ∧  𝐺  ∈  𝑇 )  ∧  𝐹  =  (  I   ↾  𝐵 ) )  →  ( 𝐹  ∘  𝐺 )  =  ( 𝐺  ∘  𝐹 ) ) |