| Step | Hyp | Ref | Expression | 
						
							| 1 |  | bracl | ⊢ ( ( 𝐴  ∈   ℋ  ∧  𝐵  ∈   ℋ )  →  ( ( bra ‘ 𝐴 ) ‘ 𝐵 )  ∈  ℂ ) | 
						
							| 2 |  | bracl | ⊢ ( ( 𝐶  ∈   ℋ  ∧  𝐷  ∈   ℋ )  →  ( ( bra ‘ 𝐶 ) ‘ 𝐷 )  ∈  ℂ ) | 
						
							| 3 |  | mulcom | ⊢ ( ( ( ( bra ‘ 𝐴 ) ‘ 𝐵 )  ∈  ℂ  ∧  ( ( bra ‘ 𝐶 ) ‘ 𝐷 )  ∈  ℂ )  →  ( ( ( bra ‘ 𝐴 ) ‘ 𝐵 )  ·  ( ( bra ‘ 𝐶 ) ‘ 𝐷 ) )  =  ( ( ( bra ‘ 𝐶 ) ‘ 𝐷 )  ·  ( ( bra ‘ 𝐴 ) ‘ 𝐵 ) ) ) | 
						
							| 4 | 1 2 3 | syl2an | ⊢ ( ( ( 𝐴  ∈   ℋ  ∧  𝐵  ∈   ℋ )  ∧  ( 𝐶  ∈   ℋ  ∧  𝐷  ∈   ℋ ) )  →  ( ( ( bra ‘ 𝐴 ) ‘ 𝐵 )  ·  ( ( bra ‘ 𝐶 ) ‘ 𝐷 ) )  =  ( ( ( bra ‘ 𝐶 ) ‘ 𝐷 )  ·  ( ( bra ‘ 𝐴 ) ‘ 𝐵 ) ) ) | 
						
							| 5 |  | bralnfn | ⊢ ( 𝐴  ∈   ℋ  →  ( bra ‘ 𝐴 )  ∈  LinFn ) | 
						
							| 6 | 5 | ad2antrr | ⊢ ( ( ( 𝐴  ∈   ℋ  ∧  𝐵  ∈   ℋ )  ∧  ( 𝐶  ∈   ℋ  ∧  𝐷  ∈   ℋ ) )  →  ( bra ‘ 𝐴 )  ∈  LinFn ) | 
						
							| 7 | 2 | adantl | ⊢ ( ( ( 𝐴  ∈   ℋ  ∧  𝐵  ∈   ℋ )  ∧  ( 𝐶  ∈   ℋ  ∧  𝐷  ∈   ℋ ) )  →  ( ( bra ‘ 𝐶 ) ‘ 𝐷 )  ∈  ℂ ) | 
						
							| 8 |  | simplr | ⊢ ( ( ( 𝐴  ∈   ℋ  ∧  𝐵  ∈   ℋ )  ∧  ( 𝐶  ∈   ℋ  ∧  𝐷  ∈   ℋ ) )  →  𝐵  ∈   ℋ ) | 
						
							| 9 |  | lnfnmul | ⊢ ( ( ( bra ‘ 𝐴 )  ∈  LinFn  ∧  ( ( bra ‘ 𝐶 ) ‘ 𝐷 )  ∈  ℂ  ∧  𝐵  ∈   ℋ )  →  ( ( bra ‘ 𝐴 ) ‘ ( ( ( bra ‘ 𝐶 ) ‘ 𝐷 )  ·ℎ  𝐵 ) )  =  ( ( ( bra ‘ 𝐶 ) ‘ 𝐷 )  ·  ( ( bra ‘ 𝐴 ) ‘ 𝐵 ) ) ) | 
						
							| 10 | 6 7 8 9 | syl3anc | ⊢ ( ( ( 𝐴  ∈   ℋ  ∧  𝐵  ∈   ℋ )  ∧  ( 𝐶  ∈   ℋ  ∧  𝐷  ∈   ℋ ) )  →  ( ( bra ‘ 𝐴 ) ‘ ( ( ( bra ‘ 𝐶 ) ‘ 𝐷 )  ·ℎ  𝐵 ) )  =  ( ( ( bra ‘ 𝐶 ) ‘ 𝐷 )  ·  ( ( bra ‘ 𝐴 ) ‘ 𝐵 ) ) ) | 
						
							| 11 | 4 10 | eqtr4d | ⊢ ( ( ( 𝐴  ∈   ℋ  ∧  𝐵  ∈   ℋ )  ∧  ( 𝐶  ∈   ℋ  ∧  𝐷  ∈   ℋ ) )  →  ( ( ( bra ‘ 𝐴 ) ‘ 𝐵 )  ·  ( ( bra ‘ 𝐶 ) ‘ 𝐷 ) )  =  ( ( bra ‘ 𝐴 ) ‘ ( ( ( bra ‘ 𝐶 ) ‘ 𝐷 )  ·ℎ  𝐵 ) ) ) |