| Step | Hyp | Ref | Expression | 
						
							| 1 |  | idn1 | ⊢ (    𝐴  ∈  𝐵    ▶    𝐴  ∈  𝐵    ) | 
						
							| 2 |  | sbcor | ⊢ ( [ 𝐴  /  𝑥 ] ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) ) | 
						
							| 3 | 2 | a1i | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑥 ] ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) ) ) | 
						
							| 4 | 1 3 | e1a | ⊢ (    𝐴  ∈  𝐵    ▶    ( [ 𝐴  /  𝑥 ] ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )    ) | 
						
							| 5 |  | df-3or | ⊢ ( ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 ) ) | 
						
							| 6 | 5 | bicomi | ⊢ ( ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  ( 𝜑  ∨  𝜓  ∨  𝜒 ) ) | 
						
							| 7 | 6 | ax-gen | ⊢ ∀ 𝑥 ( ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  ( 𝜑  ∨  𝜓  ∨  𝜒 ) ) | 
						
							| 8 |  | spsbc | ⊢ ( 𝐴  ∈  𝐵  →  ( ∀ 𝑥 ( ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  ( 𝜑  ∨  𝜓  ∨  𝜒 ) )  →  [ 𝐴  /  𝑥 ] ( ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  ( 𝜑  ∨  𝜓  ∨  𝜒 ) ) ) ) | 
						
							| 9 | 1 7 8 | e10 | ⊢ (    𝐴  ∈  𝐵    ▶    [ 𝐴  /  𝑥 ] ( ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  ( 𝜑  ∨  𝜓  ∨  𝜒 ) )    ) | 
						
							| 10 |  | sbcbig | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑥 ] ( ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  ( 𝜑  ∨  𝜓  ∨  𝜒 ) )  ↔  ( [ 𝐴  /  𝑥 ] ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 ) ) ) ) | 
						
							| 11 | 10 | biimpd | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑥 ] ( ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  ( 𝜑  ∨  𝜓  ∨  𝜒 ) )  →  ( [ 𝐴  /  𝑥 ] ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 ) ) ) ) | 
						
							| 12 | 1 9 11 | e11 | ⊢ (    𝐴  ∈  𝐵    ▶    ( [ 𝐴  /  𝑥 ] ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 ) )    ) | 
						
							| 13 |  | bitr3 | ⊢ ( ( [ 𝐴  /  𝑥 ] ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 ) )  →  ( ( [ 𝐴  /  𝑥 ] ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) ) ) ) | 
						
							| 14 | 13 | com12 | ⊢ ( ( [ 𝐴  /  𝑥 ] ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  ( ( [ 𝐴  /  𝑥 ] ( ( 𝜑  ∨  𝜓 )  ∨  𝜒 )  ↔  [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 ) )  →  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) ) ) ) | 
						
							| 15 | 4 12 14 | e11 | ⊢ (    𝐴  ∈  𝐵    ▶    ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )    ) | 
						
							| 16 |  | sbcor | ⊢ ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 ) ) | 
						
							| 17 | 16 | a1i | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 ) ) ) | 
						
							| 18 | 1 17 | e1a | ⊢ (    𝐴  ∈  𝐵    ▶    ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 ) )    ) | 
						
							| 19 |  | orbi1 | ⊢ ( ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 ) )  →  ( ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 )  ↔  ( ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) ) ) | 
						
							| 20 | 18 19 | e1a | ⊢ (    𝐴  ∈  𝐵    ▶    ( ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 )  ↔  ( ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )    ) | 
						
							| 21 |  | bibi1 | ⊢ ( ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  ( ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )  ↔  ( ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 )  ↔  ( ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) ) ) ) | 
						
							| 22 | 21 | biimprd | ⊢ ( ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  ( ( ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 )  ↔  ( ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) ) ) ) | 
						
							| 23 | 15 20 22 | e11 | ⊢ (    𝐴  ∈  𝐵    ▶    ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )    ) | 
						
							| 24 |  | df-3or | ⊢ ( ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓  ∨  [ 𝐴  /  𝑥 ] 𝜒 )  ↔  ( ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) ) | 
						
							| 25 | 24 | bicomi | ⊢ ( ( ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) ) | 
						
							| 26 |  | bibi1 | ⊢ ( ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  ( ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )  ↔  ( ( ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) ) ) ) | 
						
							| 27 | 26 | biimprd | ⊢ ( ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  ( ( ( ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓 )  ∨  [ 𝐴  /  𝑥 ] 𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )  →  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) ) ) ) | 
						
							| 28 | 23 25 27 | e10 | ⊢ (    𝐴  ∈  𝐵    ▶    ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) )    ) | 
						
							| 29 | 28 | in1 | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑥 ] ( 𝜑  ∨  𝜓  ∨  𝜒 )  ↔  ( [ 𝐴  /  𝑥 ] 𝜑  ∨  [ 𝐴  /  𝑥 ] 𝜓  ∨  [ 𝐴  /  𝑥 ] 𝜒 ) ) ) |