| Step | Hyp | Ref | Expression | 
						
							| 1 |  | simpllr | ⊢ ( ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  Fun  ( 𝐹  ↾  { 𝐴 } ) )  ∧  𝐴 𝐹 𝐵 )  →  𝐵  ∈  𝑊 ) | 
						
							| 2 |  | eleq1 | ⊢ ( 𝑥  =  𝐵  →  ( 𝑥  ∈  𝑊  ↔  𝐵  ∈  𝑊 ) ) | 
						
							| 3 | 2 | anbi2d | ⊢ ( 𝑥  =  𝐵  →  ( ( 𝐴  ∈  𝑉  ∧  𝑥  ∈  𝑊 )  ↔  ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 ) ) ) | 
						
							| 4 | 3 | anbi1d | ⊢ ( 𝑥  =  𝐵  →  ( ( ( 𝐴  ∈  𝑉  ∧  𝑥  ∈  𝑊 )  ∧  Fun  ( 𝐹  ↾  { 𝐴 } ) )  ↔  ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  Fun  ( 𝐹  ↾  { 𝐴 } ) ) ) ) | 
						
							| 5 |  | breq2 | ⊢ ( 𝑥  =  𝐵  →  ( 𝐴 𝐹 𝑥  ↔  𝐴 𝐹 𝐵 ) ) | 
						
							| 6 | 4 5 | anbi12d | ⊢ ( 𝑥  =  𝐵  →  ( ( ( ( 𝐴  ∈  𝑉  ∧  𝑥  ∈  𝑊 )  ∧  Fun  ( 𝐹  ↾  { 𝐴 } ) )  ∧  𝐴 𝐹 𝑥 )  ↔  ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  Fun  ( 𝐹  ↾  { 𝐴 } ) )  ∧  𝐴 𝐹 𝐵 ) ) ) | 
						
							| 7 |  | eqeq2 | ⊢ ( 𝑥  =  𝐵  →  ( ( 𝐹 '''' 𝐴 )  =  𝑥  ↔  ( 𝐹 '''' 𝐴 )  =  𝐵 ) ) | 
						
							| 8 | 6 7 | imbi12d | ⊢ ( 𝑥  =  𝐵  →  ( ( ( ( ( 𝐴  ∈  𝑉  ∧  𝑥  ∈  𝑊 )  ∧  Fun  ( 𝐹  ↾  { 𝐴 } ) )  ∧  𝐴 𝐹 𝑥 )  →  ( 𝐹 '''' 𝐴 )  =  𝑥 )  ↔  ( ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  Fun  ( 𝐹  ↾  { 𝐴 } ) )  ∧  𝐴 𝐹 𝐵 )  →  ( 𝐹 '''' 𝐴 )  =  𝐵 ) ) ) | 
						
							| 9 |  | id | ⊢ ( 𝐴 𝐹 𝑥  →  𝐴 𝐹 𝑥 ) | 
						
							| 10 |  | funressneu | ⊢ ( ( ( 𝐴  ∈  𝑉  ∧  𝑥  ∈  𝑊 )  ∧  Fun  ( 𝐹  ↾  { 𝐴 } )  ∧  𝐴 𝐹 𝑥 )  →  ∃! 𝑥 𝐴 𝐹 𝑥 ) | 
						
							| 11 | 10 | 3expa | ⊢ ( ( ( ( 𝐴  ∈  𝑉  ∧  𝑥  ∈  𝑊 )  ∧  Fun  ( 𝐹  ↾  { 𝐴 } ) )  ∧  𝐴 𝐹 𝑥 )  →  ∃! 𝑥 𝐴 𝐹 𝑥 ) | 
						
							| 12 |  | tz6.12-1-afv2 | ⊢ ( ( 𝐴 𝐹 𝑥  ∧  ∃! 𝑥 𝐴 𝐹 𝑥 )  →  ( 𝐹 '''' 𝐴 )  =  𝑥 ) | 
						
							| 13 | 9 11 12 | syl2an2 | ⊢ ( ( ( ( 𝐴  ∈  𝑉  ∧  𝑥  ∈  𝑊 )  ∧  Fun  ( 𝐹  ↾  { 𝐴 } ) )  ∧  𝐴 𝐹 𝑥 )  →  ( 𝐹 '''' 𝐴 )  =  𝑥 ) | 
						
							| 14 | 8 13 | vtoclg | ⊢ ( 𝐵  ∈  𝑊  →  ( ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  Fun  ( 𝐹  ↾  { 𝐴 } ) )  ∧  𝐴 𝐹 𝐵 )  →  ( 𝐹 '''' 𝐴 )  =  𝐵 ) ) | 
						
							| 15 | 1 14 | mpcom | ⊢ ( ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  Fun  ( 𝐹  ↾  { 𝐴 } ) )  ∧  𝐴 𝐹 𝐵 )  →  ( 𝐹 '''' 𝐴 )  =  𝐵 ) | 
						
							| 16 | 15 | ex | ⊢ ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  Fun  ( 𝐹  ↾  { 𝐴 } ) )  →  ( 𝐴 𝐹 𝐵  →  ( 𝐹 '''' 𝐴 )  =  𝐵 ) ) |