| Step | Hyp | Ref | Expression | 
						
							| 1 |  | reltpos | ⊢ Rel  tpos  𝐹 | 
						
							| 2 | 1 | brrelex1i | ⊢ ( 𝐴 tpos  𝐹 𝐵  →  𝐴  ∈  V ) | 
						
							| 3 | 2 | a1i | ⊢ ( 𝐵  ∈  𝑉  →  ( 𝐴 tpos  𝐹 𝐵  →  𝐴  ∈  V ) ) | 
						
							| 4 |  | elex | ⊢ ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  →  𝐴  ∈  V ) | 
						
							| 5 | 4 | adantr | ⊢ ( ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  ∪  ◡ { 𝐴 } 𝐹 𝐵 )  →  𝐴  ∈  V ) | 
						
							| 6 | 5 | a1i | ⊢ ( 𝐵  ∈  𝑉  →  ( ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  ∪  ◡ { 𝐴 } 𝐹 𝐵 )  →  𝐴  ∈  V ) ) | 
						
							| 7 |  | df-tpos | ⊢ tpos  𝐹  =  ( 𝐹  ∘  ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) ) | 
						
							| 8 | 7 | breqi | ⊢ ( 𝐴 tpos  𝐹 𝐵  ↔  𝐴 ( 𝐹  ∘  ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) ) 𝐵 ) | 
						
							| 9 |  | brcog | ⊢ ( ( 𝐴  ∈  V  ∧  𝐵  ∈  𝑉 )  →  ( 𝐴 ( 𝐹  ∘  ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) ) 𝐵  ↔  ∃ 𝑦 ( 𝐴 ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) 𝑦  ∧  𝑦 𝐹 𝐵 ) ) ) | 
						
							| 10 | 8 9 | bitrid | ⊢ ( ( 𝐴  ∈  V  ∧  𝐵  ∈  𝑉 )  →  ( 𝐴 tpos  𝐹 𝐵  ↔  ∃ 𝑦 ( 𝐴 ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) 𝑦  ∧  𝑦 𝐹 𝐵 ) ) ) | 
						
							| 11 |  | funmpt | ⊢ Fun  ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) | 
						
							| 12 |  | funbrfv2b | ⊢ ( Fun  ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } )  →  ( 𝐴 ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) 𝑦  ↔  ( 𝐴  ∈  dom  ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } )  ∧  ( ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) ‘ 𝐴 )  =  𝑦 ) ) ) | 
						
							| 13 | 11 12 | ax-mp | ⊢ ( 𝐴 ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) 𝑦  ↔  ( 𝐴  ∈  dom  ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } )  ∧  ( ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) ‘ 𝐴 )  =  𝑦 ) ) | 
						
							| 14 |  | snex | ⊢ { 𝑥 }  ∈  V | 
						
							| 15 | 14 | cnvex | ⊢ ◡ { 𝑥 }  ∈  V | 
						
							| 16 | 15 | uniex | ⊢ ∪  ◡ { 𝑥 }  ∈  V | 
						
							| 17 |  | eqid | ⊢ ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } )  =  ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) | 
						
							| 18 | 16 17 | dmmpti | ⊢ dom  ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } )  =  ( ◡ dom  𝐹  ∪  { ∅ } ) | 
						
							| 19 | 18 | eleq2i | ⊢ ( 𝐴  ∈  dom  ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } )  ↔  𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } ) ) | 
						
							| 20 |  | eqcom | ⊢ ( ( ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) ‘ 𝐴 )  =  𝑦  ↔  𝑦  =  ( ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) ‘ 𝐴 ) ) | 
						
							| 21 | 19 20 | anbi12i | ⊢ ( ( 𝐴  ∈  dom  ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } )  ∧  ( ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) ‘ 𝐴 )  =  𝑦 )  ↔  ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  𝑦  =  ( ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) ‘ 𝐴 ) ) ) | 
						
							| 22 |  | sneq | ⊢ ( 𝑥  =  𝐴  →  { 𝑥 }  =  { 𝐴 } ) | 
						
							| 23 | 22 | cnveqd | ⊢ ( 𝑥  =  𝐴  →  ◡ { 𝑥 }  =  ◡ { 𝐴 } ) | 
						
							| 24 | 23 | unieqd | ⊢ ( 𝑥  =  𝐴  →  ∪  ◡ { 𝑥 }  =  ∪  ◡ { 𝐴 } ) | 
						
							| 25 |  | snex | ⊢ { 𝐴 }  ∈  V | 
						
							| 26 | 25 | cnvex | ⊢ ◡ { 𝐴 }  ∈  V | 
						
							| 27 | 26 | uniex | ⊢ ∪  ◡ { 𝐴 }  ∈  V | 
						
							| 28 | 24 17 27 | fvmpt | ⊢ ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  →  ( ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) ‘ 𝐴 )  =  ∪  ◡ { 𝐴 } ) | 
						
							| 29 | 28 | eqeq2d | ⊢ ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  →  ( 𝑦  =  ( ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) ‘ 𝐴 )  ↔  𝑦  =  ∪  ◡ { 𝐴 } ) ) | 
						
							| 30 | 29 | pm5.32i | ⊢ ( ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  𝑦  =  ( ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) ‘ 𝐴 ) )  ↔  ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  𝑦  =  ∪  ◡ { 𝐴 } ) ) | 
						
							| 31 | 21 30 | bitri | ⊢ ( ( 𝐴  ∈  dom  ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } )  ∧  ( ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) ‘ 𝐴 )  =  𝑦 )  ↔  ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  𝑦  =  ∪  ◡ { 𝐴 } ) ) | 
						
							| 32 | 13 31 | bitri | ⊢ ( 𝐴 ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) 𝑦  ↔  ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  𝑦  =  ∪  ◡ { 𝐴 } ) ) | 
						
							| 33 | 32 | biancomi | ⊢ ( 𝐴 ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) 𝑦  ↔  ( 𝑦  =  ∪  ◡ { 𝐴 }  ∧  𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } ) ) ) | 
						
							| 34 | 33 | anbi1i | ⊢ ( ( 𝐴 ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) 𝑦  ∧  𝑦 𝐹 𝐵 )  ↔  ( ( 𝑦  =  ∪  ◡ { 𝐴 }  ∧  𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } ) )  ∧  𝑦 𝐹 𝐵 ) ) | 
						
							| 35 |  | anass | ⊢ ( ( ( 𝑦  =  ∪  ◡ { 𝐴 }  ∧  𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } ) )  ∧  𝑦 𝐹 𝐵 )  ↔  ( 𝑦  =  ∪  ◡ { 𝐴 }  ∧  ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  𝑦 𝐹 𝐵 ) ) ) | 
						
							| 36 | 34 35 | bitri | ⊢ ( ( 𝐴 ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) 𝑦  ∧  𝑦 𝐹 𝐵 )  ↔  ( 𝑦  =  ∪  ◡ { 𝐴 }  ∧  ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  𝑦 𝐹 𝐵 ) ) ) | 
						
							| 37 | 36 | exbii | ⊢ ( ∃ 𝑦 ( 𝐴 ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) 𝑦  ∧  𝑦 𝐹 𝐵 )  ↔  ∃ 𝑦 ( 𝑦  =  ∪  ◡ { 𝐴 }  ∧  ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  𝑦 𝐹 𝐵 ) ) ) | 
						
							| 38 |  | breq1 | ⊢ ( 𝑦  =  ∪  ◡ { 𝐴 }  →  ( 𝑦 𝐹 𝐵  ↔  ∪  ◡ { 𝐴 } 𝐹 𝐵 ) ) | 
						
							| 39 | 38 | anbi2d | ⊢ ( 𝑦  =  ∪  ◡ { 𝐴 }  →  ( ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  𝑦 𝐹 𝐵 )  ↔  ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  ∪  ◡ { 𝐴 } 𝐹 𝐵 ) ) ) | 
						
							| 40 | 27 39 | ceqsexv | ⊢ ( ∃ 𝑦 ( 𝑦  =  ∪  ◡ { 𝐴 }  ∧  ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  𝑦 𝐹 𝐵 ) )  ↔  ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  ∪  ◡ { 𝐴 } 𝐹 𝐵 ) ) | 
						
							| 41 | 37 40 | bitri | ⊢ ( ∃ 𝑦 ( 𝐴 ( 𝑥  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ↦  ∪  ◡ { 𝑥 } ) 𝑦  ∧  𝑦 𝐹 𝐵 )  ↔  ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  ∪  ◡ { 𝐴 } 𝐹 𝐵 ) ) | 
						
							| 42 | 10 41 | bitrdi | ⊢ ( ( 𝐴  ∈  V  ∧  𝐵  ∈  𝑉 )  →  ( 𝐴 tpos  𝐹 𝐵  ↔  ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  ∪  ◡ { 𝐴 } 𝐹 𝐵 ) ) ) | 
						
							| 43 | 42 | expcom | ⊢ ( 𝐵  ∈  𝑉  →  ( 𝐴  ∈  V  →  ( 𝐴 tpos  𝐹 𝐵  ↔  ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  ∪  ◡ { 𝐴 } 𝐹 𝐵 ) ) ) ) | 
						
							| 44 | 3 6 43 | pm5.21ndd | ⊢ ( 𝐵  ∈  𝑉  →  ( 𝐴 tpos  𝐹 𝐵  ↔  ( 𝐴  ∈  ( ◡ dom  𝐹  ∪  { ∅ } )  ∧  ∪  ◡ { 𝐴 } 𝐹 𝐵 ) ) ) |