| Step | Hyp | Ref | Expression | 
						
							| 1 |  | f1ocpbl.f | ⊢ ( 𝜑  →  𝐹 : 𝑉 –1-1-onto→ 𝑋 ) | 
						
							| 2 |  | f1of1 | ⊢ ( 𝐹 : 𝑉 –1-1-onto→ 𝑋  →  𝐹 : 𝑉 –1-1→ 𝑋 ) | 
						
							| 3 | 1 2 | syl | ⊢ ( 𝜑  →  𝐹 : 𝑉 –1-1→ 𝑋 ) | 
						
							| 4 | 3 | adantr | ⊢ ( ( 𝜑  ∧  ( 𝐴  ∈  𝐾  ∧  𝐵  ∈  𝑉  ∧  𝐶  ∈  𝑉 ) )  →  𝐹 : 𝑉 –1-1→ 𝑋 ) | 
						
							| 5 |  | simpr2 | ⊢ ( ( 𝜑  ∧  ( 𝐴  ∈  𝐾  ∧  𝐵  ∈  𝑉  ∧  𝐶  ∈  𝑉 ) )  →  𝐵  ∈  𝑉 ) | 
						
							| 6 |  | simpr3 | ⊢ ( ( 𝜑  ∧  ( 𝐴  ∈  𝐾  ∧  𝐵  ∈  𝑉  ∧  𝐶  ∈  𝑉 ) )  →  𝐶  ∈  𝑉 ) | 
						
							| 7 |  | f1fveq | ⊢ ( ( 𝐹 : 𝑉 –1-1→ 𝑋  ∧  ( 𝐵  ∈  𝑉  ∧  𝐶  ∈  𝑉 ) )  →  ( ( 𝐹 ‘ 𝐵 )  =  ( 𝐹 ‘ 𝐶 )  ↔  𝐵  =  𝐶 ) ) | 
						
							| 8 | 4 5 6 7 | syl12anc | ⊢ ( ( 𝜑  ∧  ( 𝐴  ∈  𝐾  ∧  𝐵  ∈  𝑉  ∧  𝐶  ∈  𝑉 ) )  →  ( ( 𝐹 ‘ 𝐵 )  =  ( 𝐹 ‘ 𝐶 )  ↔  𝐵  =  𝐶 ) ) | 
						
							| 9 |  | oveq2 | ⊢ ( 𝐵  =  𝐶  →  ( 𝐴  +  𝐵 )  =  ( 𝐴  +  𝐶 ) ) | 
						
							| 10 | 9 | fveq2d | ⊢ ( 𝐵  =  𝐶  →  ( 𝐹 ‘ ( 𝐴  +  𝐵 ) )  =  ( 𝐹 ‘ ( 𝐴  +  𝐶 ) ) ) | 
						
							| 11 | 8 10 | biimtrdi | ⊢ ( ( 𝜑  ∧  ( 𝐴  ∈  𝐾  ∧  𝐵  ∈  𝑉  ∧  𝐶  ∈  𝑉 ) )  →  ( ( 𝐹 ‘ 𝐵 )  =  ( 𝐹 ‘ 𝐶 )  →  ( 𝐹 ‘ ( 𝐴  +  𝐵 ) )  =  ( 𝐹 ‘ ( 𝐴  +  𝐶 ) ) ) ) |