| Step | Hyp | Ref | Expression | 
						
							| 1 |  | ordtNEW.b | ⊢ 𝐵  =  ( Base ‘ 𝐾 ) | 
						
							| 2 |  | ordtNEW.l | ⊢  ≤   =  ( ( le ‘ 𝐾 )  ∩  ( 𝐵  ×  𝐵 ) ) | 
						
							| 3 |  | ordtposval.e | ⊢ 𝐸  =  ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑦  ≤  𝑥 } ) | 
						
							| 4 |  | ordtposval.f | ⊢ 𝐹  =  ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑥  ≤  𝑦 } ) | 
						
							| 5 | 1 2 | prsdm | ⊢ ( 𝐾  ∈   Proset   →  dom   ≤   =  𝐵 ) | 
						
							| 6 | 5 | sneqd | ⊢ ( 𝐾  ∈   Proset   →  { dom   ≤  }  =  { 𝐵 } ) | 
						
							| 7 |  | biidd | ⊢ ( 𝐾  ∈   Proset   →  ( ¬  𝑦  ≤  𝑥  ↔  ¬  𝑦  ≤  𝑥 ) ) | 
						
							| 8 | 5 7 | rabeqbidv | ⊢ ( 𝐾  ∈   Proset   →  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑦  ≤  𝑥 }  =  { 𝑦  ∈  𝐵  ∣  ¬  𝑦  ≤  𝑥 } ) | 
						
							| 9 | 5 8 | mpteq12dv | ⊢ ( 𝐾  ∈   Proset   →  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑦  ≤  𝑥 } )  =  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑦  ≤  𝑥 } ) ) | 
						
							| 10 | 9 | rneqd | ⊢ ( 𝐾  ∈   Proset   →  ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑦  ≤  𝑥 } )  =  ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑦  ≤  𝑥 } ) ) | 
						
							| 11 |  | biidd | ⊢ ( 𝐾  ∈   Proset   →  ( ¬  𝑥  ≤  𝑦  ↔  ¬  𝑥  ≤  𝑦 ) ) | 
						
							| 12 | 5 11 | rabeqbidv | ⊢ ( 𝐾  ∈   Proset   →  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑥  ≤  𝑦 }  =  { 𝑦  ∈  𝐵  ∣  ¬  𝑥  ≤  𝑦 } ) | 
						
							| 13 | 5 12 | mpteq12dv | ⊢ ( 𝐾  ∈   Proset   →  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑥  ≤  𝑦 } )  =  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑥  ≤  𝑦 } ) ) | 
						
							| 14 | 13 | rneqd | ⊢ ( 𝐾  ∈   Proset   →  ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑥  ≤  𝑦 } )  =  ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑥  ≤  𝑦 } ) ) | 
						
							| 15 | 10 14 | uneq12d | ⊢ ( 𝐾  ∈   Proset   →  ( ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑦  ≤  𝑥 } )  ∪  ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑥  ≤  𝑦 } ) )  =  ( ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑦  ≤  𝑥 } )  ∪  ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑥  ≤  𝑦 } ) ) ) | 
						
							| 16 | 6 15 | uneq12d | ⊢ ( 𝐾  ∈   Proset   →  ( { dom   ≤  }  ∪  ( ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑦  ≤  𝑥 } )  ∪  ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑥  ≤  𝑦 } ) ) )  =  ( { 𝐵 }  ∪  ( ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑦  ≤  𝑥 } )  ∪  ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑥  ≤  𝑦 } ) ) ) ) | 
						
							| 17 | 16 | unieqd | ⊢ ( 𝐾  ∈   Proset   →  ∪  ( { dom   ≤  }  ∪  ( ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑦  ≤  𝑥 } )  ∪  ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑥  ≤  𝑦 } ) ) )  =  ∪  ( { 𝐵 }  ∪  ( ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑦  ≤  𝑥 } )  ∪  ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑥  ≤  𝑦 } ) ) ) ) | 
						
							| 18 |  | fvex | ⊢ ( le ‘ 𝐾 )  ∈  V | 
						
							| 19 | 18 | inex1 | ⊢ ( ( le ‘ 𝐾 )  ∩  ( 𝐵  ×  𝐵 ) )  ∈  V | 
						
							| 20 | 2 19 | eqeltri | ⊢  ≤   ∈  V | 
						
							| 21 |  | eqid | ⊢ dom   ≤   =  dom   ≤ | 
						
							| 22 |  | eqid | ⊢ ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑦  ≤  𝑥 } )  =  ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑦  ≤  𝑥 } ) | 
						
							| 23 |  | eqid | ⊢ ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑥  ≤  𝑦 } )  =  ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑥  ≤  𝑦 } ) | 
						
							| 24 | 21 22 23 | ordtuni | ⊢ (  ≤   ∈  V  →  dom   ≤   =  ∪  ( { dom   ≤  }  ∪  ( ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑦  ≤  𝑥 } )  ∪  ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑥  ≤  𝑦 } ) ) ) ) | 
						
							| 25 | 20 24 | ax-mp | ⊢ dom   ≤   =  ∪  ( { dom   ≤  }  ∪  ( ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑦  ≤  𝑥 } )  ∪  ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑥  ≤  𝑦 } ) ) ) | 
						
							| 26 | 5 25 | eqtr3di | ⊢ ( 𝐾  ∈   Proset   →  𝐵  =  ∪  ( { dom   ≤  }  ∪  ( ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑦  ≤  𝑥 } )  ∪  ran  ( 𝑥  ∈  dom   ≤   ↦  { 𝑦  ∈  dom   ≤   ∣  ¬  𝑥  ≤  𝑦 } ) ) ) ) | 
						
							| 27 | 3 4 | uneq12i | ⊢ ( 𝐸  ∪  𝐹 )  =  ( ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑦  ≤  𝑥 } )  ∪  ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑥  ≤  𝑦 } ) ) | 
						
							| 28 | 27 | a1i | ⊢ ( 𝐾  ∈   Proset   →  ( 𝐸  ∪  𝐹 )  =  ( ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑦  ≤  𝑥 } )  ∪  ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑥  ≤  𝑦 } ) ) ) | 
						
							| 29 | 28 | uneq2d | ⊢ ( 𝐾  ∈   Proset   →  ( { 𝐵 }  ∪  ( 𝐸  ∪  𝐹 ) )  =  ( { 𝐵 }  ∪  ( ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑦  ≤  𝑥 } )  ∪  ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑥  ≤  𝑦 } ) ) ) ) | 
						
							| 30 | 29 | unieqd | ⊢ ( 𝐾  ∈   Proset   →  ∪  ( { 𝐵 }  ∪  ( 𝐸  ∪  𝐹 ) )  =  ∪  ( { 𝐵 }  ∪  ( ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑦  ≤  𝑥 } )  ∪  ran  ( 𝑥  ∈  𝐵  ↦  { 𝑦  ∈  𝐵  ∣  ¬  𝑥  ≤  𝑦 } ) ) ) ) | 
						
							| 31 | 17 26 30 | 3eqtr4d | ⊢ ( 𝐾  ∈   Proset   →  𝐵  =  ∪  ( { 𝐵 }  ∪  ( 𝐸  ∪  𝐹 ) ) ) |