| Step | Hyp | Ref | Expression | 
						
							| 1 |  | idn1 | ⊢ (    ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜃  ↔  𝜏 ) )    ▶    ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜃  ↔  𝜏 ) )    ) | 
						
							| 2 |  | bicom | ⊢ ( ( 𝜃  ↔  𝜏 )  ↔  ( 𝜏  ↔  𝜃 ) ) | 
						
							| 3 |  | imbi2 | ⊢ ( ( ( 𝜃  ↔  𝜏 )  ↔  ( 𝜏  ↔  𝜃 ) )  →  ( ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜃  ↔  𝜏 ) )  ↔  ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜏  ↔  𝜃 ) ) ) ) | 
						
							| 4 | 3 | biimpcd | ⊢ ( ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜃  ↔  𝜏 ) )  →  ( ( ( 𝜃  ↔  𝜏 )  ↔  ( 𝜏  ↔  𝜃 ) )  →  ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜏  ↔  𝜃 ) ) ) ) | 
						
							| 5 | 1 2 4 | e10 | ⊢ (    ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜃  ↔  𝜏 ) )    ▶    ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜏  ↔  𝜃 ) )    ) | 
						
							| 6 |  | 3impexp | ⊢ ( ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜏  ↔  𝜃 ) )  ↔  ( 𝜑  →  ( 𝜓  →  ( 𝜒  →  ( 𝜏  ↔  𝜃 ) ) ) ) ) | 
						
							| 7 | 6 | biimpi | ⊢ ( ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜏  ↔  𝜃 ) )  →  ( 𝜑  →  ( 𝜓  →  ( 𝜒  →  ( 𝜏  ↔  𝜃 ) ) ) ) ) | 
						
							| 8 | 5 7 | e1a | ⊢ (    ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜃  ↔  𝜏 ) )    ▶    ( 𝜑  →  ( 𝜓  →  ( 𝜒  →  ( 𝜏  ↔  𝜃 ) ) ) )    ) | 
						
							| 9 | 8 | in1 | ⊢ ( ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜃  ↔  𝜏 ) )  →  ( 𝜑  →  ( 𝜓  →  ( 𝜒  →  ( 𝜏  ↔  𝜃 ) ) ) ) ) | 
						
							| 10 |  | idn1 | ⊢ (    ( 𝜑  →  ( 𝜓  →  ( 𝜒  →  ( 𝜏  ↔  𝜃 ) ) ) )    ▶    ( 𝜑  →  ( 𝜓  →  ( 𝜒  →  ( 𝜏  ↔  𝜃 ) ) ) )    ) | 
						
							| 11 | 6 | biimpri | ⊢ ( ( 𝜑  →  ( 𝜓  →  ( 𝜒  →  ( 𝜏  ↔  𝜃 ) ) ) )  →  ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜏  ↔  𝜃 ) ) ) | 
						
							| 12 | 10 11 | e1a | ⊢ (    ( 𝜑  →  ( 𝜓  →  ( 𝜒  →  ( 𝜏  ↔  𝜃 ) ) ) )    ▶    ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜏  ↔  𝜃 ) )    ) | 
						
							| 13 | 3 | biimprcd | ⊢ ( ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜏  ↔  𝜃 ) )  →  ( ( ( 𝜃  ↔  𝜏 )  ↔  ( 𝜏  ↔  𝜃 ) )  →  ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜃  ↔  𝜏 ) ) ) ) | 
						
							| 14 | 12 2 13 | e10 | ⊢ (    ( 𝜑  →  ( 𝜓  →  ( 𝜒  →  ( 𝜏  ↔  𝜃 ) ) ) )    ▶    ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜃  ↔  𝜏 ) )    ) | 
						
							| 15 | 14 | in1 | ⊢ ( ( 𝜑  →  ( 𝜓  →  ( 𝜒  →  ( 𝜏  ↔  𝜃 ) ) ) )  →  ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜃  ↔  𝜏 ) ) ) | 
						
							| 16 |  | impbi | ⊢ ( ( ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜃  ↔  𝜏 ) )  →  ( 𝜑  →  ( 𝜓  →  ( 𝜒  →  ( 𝜏  ↔  𝜃 ) ) ) ) )  →  ( ( ( 𝜑  →  ( 𝜓  →  ( 𝜒  →  ( 𝜏  ↔  𝜃 ) ) ) )  →  ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜃  ↔  𝜏 ) ) )  →  ( ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜃  ↔  𝜏 ) )  ↔  ( 𝜑  →  ( 𝜓  →  ( 𝜒  →  ( 𝜏  ↔  𝜃 ) ) ) ) ) ) ) | 
						
							| 17 | 9 15 16 | e00 | ⊢ ( ( ( 𝜑  ∧  𝜓  ∧  𝜒 )  →  ( 𝜃  ↔  𝜏 ) )  ↔  ( 𝜑  →  ( 𝜓  →  ( 𝜒  →  ( 𝜏  ↔  𝜃 ) ) ) ) ) |