| Step | Hyp | Ref | Expression | 
						
							| 1 |  | idn2 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ▶    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ) | 
						
							| 2 |  | simpr | ⊢ ( ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )  →  𝑦  ∈  ∪  𝐴 ) | 
						
							| 3 | 1 2 | e2 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ▶    𝑦  ∈  ∪  𝐴    ) | 
						
							| 4 |  | eluni | ⊢ ( 𝑦  ∈  ∪  𝐴  ↔  ∃ 𝑞 ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 ) ) | 
						
							| 5 | 4 | biimpi | ⊢ ( 𝑦  ∈  ∪  𝐴  →  ∃ 𝑞 ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 ) ) | 
						
							| 6 | 3 5 | e2 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ▶    ∃ 𝑞 ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )    ) | 
						
							| 7 |  | simpl | ⊢ ( ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )  →  𝑧  ∈  𝑦 ) | 
						
							| 8 | 1 7 | e2 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ▶    𝑧  ∈  𝑦    ) | 
						
							| 9 |  | idn3 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ,    ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )    ▶    ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )    ) | 
						
							| 10 |  | simpl | ⊢ ( ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )  →  𝑦  ∈  𝑞 ) | 
						
							| 11 | 9 10 | e3 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ,    ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )    ▶    𝑦  ∈  𝑞    ) | 
						
							| 12 |  | simpr | ⊢ ( ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )  →  𝑞  ∈  𝐴 ) | 
						
							| 13 | 9 12 | e3 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ,    ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )    ▶    𝑞  ∈  𝐴    ) | 
						
							| 14 |  | idn1 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ▶    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ) | 
						
							| 15 |  | rspsbc | ⊢ ( 𝑞  ∈  𝐴  →  ( ∀ 𝑥  ∈  𝐴 Tr  𝑥  →  [ 𝑞  /  𝑥 ] Tr  𝑥 ) ) | 
						
							| 16 | 15 | com12 | ⊢ ( ∀ 𝑥  ∈  𝐴 Tr  𝑥  →  ( 𝑞  ∈  𝐴  →  [ 𝑞  /  𝑥 ] Tr  𝑥 ) ) | 
						
							| 17 | 14 13 16 | e13 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ,    ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )    ▶    [ 𝑞  /  𝑥 ] Tr  𝑥    ) | 
						
							| 18 |  | trsbc | ⊢ ( 𝑞  ∈  𝐴  →  ( [ 𝑞  /  𝑥 ] Tr  𝑥  ↔  Tr  𝑞 ) ) | 
						
							| 19 | 18 | biimpd | ⊢ ( 𝑞  ∈  𝐴  →  ( [ 𝑞  /  𝑥 ] Tr  𝑥  →  Tr  𝑞 ) ) | 
						
							| 20 | 13 17 19 | e33 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ,    ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )    ▶    Tr  𝑞    ) | 
						
							| 21 |  | trel | ⊢ ( Tr  𝑞  →  ( ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  𝑞 )  →  𝑧  ∈  𝑞 ) ) | 
						
							| 22 | 21 | expdcom | ⊢ ( 𝑧  ∈  𝑦  →  ( 𝑦  ∈  𝑞  →  ( Tr  𝑞  →  𝑧  ∈  𝑞 ) ) ) | 
						
							| 23 | 8 11 20 22 | e233 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ,    ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )    ▶    𝑧  ∈  𝑞    ) | 
						
							| 24 |  | elunii | ⊢ ( ( 𝑧  ∈  𝑞  ∧  𝑞  ∈  𝐴 )  →  𝑧  ∈  ∪  𝐴 ) | 
						
							| 25 | 24 | ex | ⊢ ( 𝑧  ∈  𝑞  →  ( 𝑞  ∈  𝐴  →  𝑧  ∈  ∪  𝐴 ) ) | 
						
							| 26 | 23 13 25 | e33 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ,    ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )    ▶    𝑧  ∈  ∪  𝐴    ) | 
						
							| 27 | 26 | in3 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ▶    ( ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )  →  𝑧  ∈  ∪  𝐴 )    ) | 
						
							| 28 | 27 | gen21 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ▶    ∀ 𝑞 ( ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )  →  𝑧  ∈  ∪  𝐴 )    ) | 
						
							| 29 |  | 19.23v | ⊢ ( ∀ 𝑞 ( ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )  →  𝑧  ∈  ∪  𝐴 )  ↔  ( ∃ 𝑞 ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )  →  𝑧  ∈  ∪  𝐴 ) ) | 
						
							| 30 | 29 | biimpi | ⊢ ( ∀ 𝑞 ( ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )  →  𝑧  ∈  ∪  𝐴 )  →  ( ∃ 𝑞 ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )  →  𝑧  ∈  ∪  𝐴 ) ) | 
						
							| 31 | 28 30 | e2 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ▶    ( ∃ 𝑞 ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )  →  𝑧  ∈  ∪  𝐴 )    ) | 
						
							| 32 |  | pm2.27 | ⊢ ( ∃ 𝑞 ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )  →  ( ( ∃ 𝑞 ( 𝑦  ∈  𝑞  ∧  𝑞  ∈  𝐴 )  →  𝑧  ∈  ∪  𝐴 )  →  𝑧  ∈  ∪  𝐴 ) ) | 
						
							| 33 | 6 31 32 | e22 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ,    ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )    ▶    𝑧  ∈  ∪  𝐴    ) | 
						
							| 34 | 33 | in2 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ▶    ( ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )  →  𝑧  ∈  ∪  𝐴 )    ) | 
						
							| 35 | 34 | gen12 | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ▶    ∀ 𝑧 ∀ 𝑦 ( ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )  →  𝑧  ∈  ∪  𝐴 )    ) | 
						
							| 36 |  | dftr2 | ⊢ ( Tr  ∪  𝐴  ↔  ∀ 𝑧 ∀ 𝑦 ( ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )  →  𝑧  ∈  ∪  𝐴 ) ) | 
						
							| 37 | 36 | biimpri | ⊢ ( ∀ 𝑧 ∀ 𝑦 ( ( 𝑧  ∈  𝑦  ∧  𝑦  ∈  ∪  𝐴 )  →  𝑧  ∈  ∪  𝐴 )  →  Tr  ∪  𝐴 ) | 
						
							| 38 | 35 37 | e1a | ⊢ (    ∀ 𝑥  ∈  𝐴 Tr  𝑥    ▶    Tr  ∪  𝐴    ) | 
						
							| 39 | 38 | in1 | ⊢ ( ∀ 𝑥  ∈  𝐴 Tr  𝑥  →  Tr  ∪  𝐴 ) |