| Step | Hyp | Ref | Expression | 
						
							| 1 |  | sbcor | ⊢ ( [ 𝐴  /  𝑦 ] ( ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥 )  ∨  𝑥  =  𝑦 )  ↔  ( [ 𝐴  /  𝑦 ] ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥 )  ∨  [ 𝐴  /  𝑦 ] 𝑥  =  𝑦 ) ) | 
						
							| 2 | 1 | a1i | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑦 ] ( ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥 )  ∨  𝑥  =  𝑦 )  ↔  ( [ 𝐴  /  𝑦 ] ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥 )  ∨  [ 𝐴  /  𝑦 ] 𝑥  =  𝑦 ) ) ) | 
						
							| 3 |  | df-3or | ⊢ ( ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥  ∨  𝑥  =  𝑦 )  ↔  ( ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥 )  ∨  𝑥  =  𝑦 ) ) | 
						
							| 4 | 3 | bicomi | ⊢ ( ( ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥 )  ∨  𝑥  =  𝑦 )  ↔  ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥  ∨  𝑥  =  𝑦 ) ) | 
						
							| 5 | 4 | sbcbii | ⊢ ( [ 𝐴  /  𝑦 ] ( ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥 )  ∨  𝑥  =  𝑦 )  ↔  [ 𝐴  /  𝑦 ] ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥  ∨  𝑥  =  𝑦 ) ) | 
						
							| 6 | 5 | a1i | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑦 ] ( ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥 )  ∨  𝑥  =  𝑦 )  ↔  [ 𝐴  /  𝑦 ] ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥  ∨  𝑥  =  𝑦 ) ) ) | 
						
							| 7 |  | sbcor | ⊢ ( [ 𝐴  /  𝑦 ] ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥 )  ↔  ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ∨  [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥 ) ) | 
						
							| 8 | 7 | a1i | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑦 ] ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥 )  ↔  ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ∨  [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥 ) ) ) | 
						
							| 9 | 8 | orbi1d | ⊢ ( 𝐴  ∈  𝐵  →  ( ( [ 𝐴  /  𝑦 ] ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥 )  ∨  [ 𝐴  /  𝑦 ] 𝑥  =  𝑦 )  ↔  ( ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ∨  [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥 )  ∨  [ 𝐴  /  𝑦 ] 𝑥  =  𝑦 ) ) ) | 
						
							| 10 | 2 6 9 | 3bitr3d | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑦 ] ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥  ∨  𝑥  =  𝑦 )  ↔  ( ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ∨  [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥 )  ∨  [ 𝐴  /  𝑦 ] 𝑥  =  𝑦 ) ) ) | 
						
							| 11 |  | df-3or | ⊢ ( ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ∨  [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥  ∨  [ 𝐴  /  𝑦 ] 𝑥  =  𝑦 )  ↔  ( ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ∨  [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥 )  ∨  [ 𝐴  /  𝑦 ] 𝑥  =  𝑦 ) ) | 
						
							| 12 | 10 11 | bitr4di | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑦 ] ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥  ∨  𝑥  =  𝑦 )  ↔  ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ∨  [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥  ∨  [ 𝐴  /  𝑦 ] 𝑥  =  𝑦 ) ) ) | 
						
							| 13 | 12 | dfvd1ir | ⊢ (    𝐴  ∈  𝐵    ▶    ( [ 𝐴  /  𝑦 ] ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥  ∨  𝑥  =  𝑦 )  ↔  ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ∨  [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥  ∨  [ 𝐴  /  𝑦 ] 𝑥  =  𝑦 ) )    ) | 
						
							| 14 |  | sbcel2gv | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ↔  𝑥  ∈  𝐴 ) ) | 
						
							| 15 | 14 | dfvd1ir | ⊢ (    𝐴  ∈  𝐵    ▶    ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ↔  𝑥  ∈  𝐴 )    ) | 
						
							| 16 |  | sbcel1v | ⊢ ( [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥  ↔  𝐴  ∈  𝑥 ) | 
						
							| 17 |  | eqsbc2 | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑦 ] 𝑥  =  𝑦  ↔  𝑥  =  𝐴 ) ) | 
						
							| 18 | 17 | dfvd1ir | ⊢ (    𝐴  ∈  𝐵    ▶    ( [ 𝐴  /  𝑦 ] 𝑥  =  𝑦  ↔  𝑥  =  𝐴 )    ) | 
						
							| 19 |  | 3orbi123 | ⊢ ( ( ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ↔  𝑥  ∈  𝐴 )  ∧  ( [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥  ↔  𝐴  ∈  𝑥 )  ∧  ( [ 𝐴  /  𝑦 ] 𝑥  =  𝑦  ↔  𝑥  =  𝐴 ) )  →  ( ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ∨  [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥  ∨  [ 𝐴  /  𝑦 ] 𝑥  =  𝑦 )  ↔  ( 𝑥  ∈  𝐴  ∨  𝐴  ∈  𝑥  ∨  𝑥  =  𝐴 ) ) ) | 
						
							| 20 | 19 | 3impexpbicomi | ⊢ ( ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ↔  𝑥  ∈  𝐴 )  →  ( ( [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥  ↔  𝐴  ∈  𝑥 )  →  ( ( [ 𝐴  /  𝑦 ] 𝑥  =  𝑦  ↔  𝑥  =  𝐴 )  →  ( ( 𝑥  ∈  𝐴  ∨  𝐴  ∈  𝑥  ∨  𝑥  =  𝐴 )  ↔  ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ∨  [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥  ∨  [ 𝐴  /  𝑦 ] 𝑥  =  𝑦 ) ) ) ) ) | 
						
							| 21 | 15 16 18 20 | e101 | ⊢ (    𝐴  ∈  𝐵    ▶    ( ( 𝑥  ∈  𝐴  ∨  𝐴  ∈  𝑥  ∨  𝑥  =  𝐴 )  ↔  ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ∨  [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥  ∨  [ 𝐴  /  𝑦 ] 𝑥  =  𝑦 ) )    ) | 
						
							| 22 |  | biantr | ⊢ ( ( ( [ 𝐴  /  𝑦 ] ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥  ∨  𝑥  =  𝑦 )  ↔  ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ∨  [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥  ∨  [ 𝐴  /  𝑦 ] 𝑥  =  𝑦 ) )  ∧  ( ( 𝑥  ∈  𝐴  ∨  𝐴  ∈  𝑥  ∨  𝑥  =  𝐴 )  ↔  ( [ 𝐴  /  𝑦 ] 𝑥  ∈  𝑦  ∨  [ 𝐴  /  𝑦 ] 𝑦  ∈  𝑥  ∨  [ 𝐴  /  𝑦 ] 𝑥  =  𝑦 ) ) )  →  ( [ 𝐴  /  𝑦 ] ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥  ∨  𝑥  =  𝑦 )  ↔  ( 𝑥  ∈  𝐴  ∨  𝐴  ∈  𝑥  ∨  𝑥  =  𝐴 ) ) ) | 
						
							| 23 | 13 21 22 | e11an | ⊢ (    𝐴  ∈  𝐵    ▶    ( [ 𝐴  /  𝑦 ] ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥  ∨  𝑥  =  𝑦 )  ↔  ( 𝑥  ∈  𝐴  ∨  𝐴  ∈  𝑥  ∨  𝑥  =  𝐴 ) )    ) | 
						
							| 24 | 23 | in1 | ⊢ ( 𝐴  ∈  𝐵  →  ( [ 𝐴  /  𝑦 ] ( 𝑥  ∈  𝑦  ∨  𝑦  ∈  𝑥  ∨  𝑥  =  𝑦 )  ↔  ( 𝑥  ∈  𝐴  ∨  𝐴  ∈  𝑥  ∨  𝑥  =  𝐴 ) ) ) |