| Step | Hyp | Ref | Expression | 
						
							| 1 |  | oveq2 | ⊢ ( 𝑦  =  𝐴  →  ( ( 𝑥  ·ih  𝑧 )  ·ℎ  𝑦 )  =  ( ( 𝑥  ·ih  𝑧 )  ·ℎ  𝐴 ) ) | 
						
							| 2 | 1 | mpteq2dv | ⊢ ( 𝑦  =  𝐴  →  ( 𝑥  ∈   ℋ  ↦  ( ( 𝑥  ·ih  𝑧 )  ·ℎ  𝑦 ) )  =  ( 𝑥  ∈   ℋ  ↦  ( ( 𝑥  ·ih  𝑧 )  ·ℎ  𝐴 ) ) ) | 
						
							| 3 |  | oveq2 | ⊢ ( 𝑧  =  𝐵  →  ( 𝑥  ·ih  𝑧 )  =  ( 𝑥  ·ih  𝐵 ) ) | 
						
							| 4 | 3 | oveq1d | ⊢ ( 𝑧  =  𝐵  →  ( ( 𝑥  ·ih  𝑧 )  ·ℎ  𝐴 )  =  ( ( 𝑥  ·ih  𝐵 )  ·ℎ  𝐴 ) ) | 
						
							| 5 | 4 | mpteq2dv | ⊢ ( 𝑧  =  𝐵  →  ( 𝑥  ∈   ℋ  ↦  ( ( 𝑥  ·ih  𝑧 )  ·ℎ  𝐴 ) )  =  ( 𝑥  ∈   ℋ  ↦  ( ( 𝑥  ·ih  𝐵 )  ·ℎ  𝐴 ) ) ) | 
						
							| 6 |  | df-kb | ⊢  ketbra   =  ( 𝑦  ∈   ℋ ,  𝑧  ∈   ℋ  ↦  ( 𝑥  ∈   ℋ  ↦  ( ( 𝑥  ·ih  𝑧 )  ·ℎ  𝑦 ) ) ) | 
						
							| 7 |  | ax-hilex | ⊢  ℋ  ∈  V | 
						
							| 8 | 7 | mptex | ⊢ ( 𝑥  ∈   ℋ  ↦  ( ( 𝑥  ·ih  𝐵 )  ·ℎ  𝐴 ) )  ∈  V | 
						
							| 9 | 2 5 6 8 | ovmpo | ⊢ ( ( 𝐴  ∈   ℋ  ∧  𝐵  ∈   ℋ )  →  ( 𝐴  ketbra  𝐵 )  =  ( 𝑥  ∈   ℋ  ↦  ( ( 𝑥  ·ih  𝐵 )  ·ℎ  𝐴 ) ) ) |