| Step | Hyp | Ref | Expression | 
						
							| 0 |  | cbtwn | ⊢  Btwn | 
						
							| 1 |  | vx | ⊢ 𝑥 | 
						
							| 2 |  | vz | ⊢ 𝑧 | 
						
							| 3 |  | vy | ⊢ 𝑦 | 
						
							| 4 |  | vn | ⊢ 𝑛 | 
						
							| 5 |  | cn | ⊢ ℕ | 
						
							| 6 | 1 | cv | ⊢ 𝑥 | 
						
							| 7 |  | cee | ⊢ 𝔼 | 
						
							| 8 | 4 | cv | ⊢ 𝑛 | 
						
							| 9 | 8 7 | cfv | ⊢ ( 𝔼 ‘ 𝑛 ) | 
						
							| 10 | 6 9 | wcel | ⊢ 𝑥  ∈  ( 𝔼 ‘ 𝑛 ) | 
						
							| 11 | 2 | cv | ⊢ 𝑧 | 
						
							| 12 | 11 9 | wcel | ⊢ 𝑧  ∈  ( 𝔼 ‘ 𝑛 ) | 
						
							| 13 | 3 | cv | ⊢ 𝑦 | 
						
							| 14 | 13 9 | wcel | ⊢ 𝑦  ∈  ( 𝔼 ‘ 𝑛 ) | 
						
							| 15 | 10 12 14 | w3a | ⊢ ( 𝑥  ∈  ( 𝔼 ‘ 𝑛 )  ∧  𝑧  ∈  ( 𝔼 ‘ 𝑛 )  ∧  𝑦  ∈  ( 𝔼 ‘ 𝑛 ) ) | 
						
							| 16 |  | vt | ⊢ 𝑡 | 
						
							| 17 |  | cc0 | ⊢ 0 | 
						
							| 18 |  | cicc | ⊢ [,] | 
						
							| 19 |  | c1 | ⊢ 1 | 
						
							| 20 | 17 19 18 | co | ⊢ ( 0 [,] 1 ) | 
						
							| 21 |  | vi | ⊢ 𝑖 | 
						
							| 22 |  | cfz | ⊢ ... | 
						
							| 23 | 19 8 22 | co | ⊢ ( 1 ... 𝑛 ) | 
						
							| 24 | 21 | cv | ⊢ 𝑖 | 
						
							| 25 | 24 13 | cfv | ⊢ ( 𝑦 ‘ 𝑖 ) | 
						
							| 26 |  | cmin | ⊢  − | 
						
							| 27 | 16 | cv | ⊢ 𝑡 | 
						
							| 28 | 19 27 26 | co | ⊢ ( 1  −  𝑡 ) | 
						
							| 29 |  | cmul | ⊢  · | 
						
							| 30 | 24 6 | cfv | ⊢ ( 𝑥 ‘ 𝑖 ) | 
						
							| 31 | 28 30 29 | co | ⊢ ( ( 1  −  𝑡 )  ·  ( 𝑥 ‘ 𝑖 ) ) | 
						
							| 32 |  | caddc | ⊢  + | 
						
							| 33 | 24 11 | cfv | ⊢ ( 𝑧 ‘ 𝑖 ) | 
						
							| 34 | 27 33 29 | co | ⊢ ( 𝑡  ·  ( 𝑧 ‘ 𝑖 ) ) | 
						
							| 35 | 31 34 32 | co | ⊢ ( ( ( 1  −  𝑡 )  ·  ( 𝑥 ‘ 𝑖 ) )  +  ( 𝑡  ·  ( 𝑧 ‘ 𝑖 ) ) ) | 
						
							| 36 | 25 35 | wceq | ⊢ ( 𝑦 ‘ 𝑖 )  =  ( ( ( 1  −  𝑡 )  ·  ( 𝑥 ‘ 𝑖 ) )  +  ( 𝑡  ·  ( 𝑧 ‘ 𝑖 ) ) ) | 
						
							| 37 | 36 21 23 | wral | ⊢ ∀ 𝑖  ∈  ( 1 ... 𝑛 ) ( 𝑦 ‘ 𝑖 )  =  ( ( ( 1  −  𝑡 )  ·  ( 𝑥 ‘ 𝑖 ) )  +  ( 𝑡  ·  ( 𝑧 ‘ 𝑖 ) ) ) | 
						
							| 38 | 37 16 20 | wrex | ⊢ ∃ 𝑡  ∈  ( 0 [,] 1 ) ∀ 𝑖  ∈  ( 1 ... 𝑛 ) ( 𝑦 ‘ 𝑖 )  =  ( ( ( 1  −  𝑡 )  ·  ( 𝑥 ‘ 𝑖 ) )  +  ( 𝑡  ·  ( 𝑧 ‘ 𝑖 ) ) ) | 
						
							| 39 | 15 38 | wa | ⊢ ( ( 𝑥  ∈  ( 𝔼 ‘ 𝑛 )  ∧  𝑧  ∈  ( 𝔼 ‘ 𝑛 )  ∧  𝑦  ∈  ( 𝔼 ‘ 𝑛 ) )  ∧  ∃ 𝑡  ∈  ( 0 [,] 1 ) ∀ 𝑖  ∈  ( 1 ... 𝑛 ) ( 𝑦 ‘ 𝑖 )  =  ( ( ( 1  −  𝑡 )  ·  ( 𝑥 ‘ 𝑖 ) )  +  ( 𝑡  ·  ( 𝑧 ‘ 𝑖 ) ) ) ) | 
						
							| 40 | 39 4 5 | wrex | ⊢ ∃ 𝑛  ∈  ℕ ( ( 𝑥  ∈  ( 𝔼 ‘ 𝑛 )  ∧  𝑧  ∈  ( 𝔼 ‘ 𝑛 )  ∧  𝑦  ∈  ( 𝔼 ‘ 𝑛 ) )  ∧  ∃ 𝑡  ∈  ( 0 [,] 1 ) ∀ 𝑖  ∈  ( 1 ... 𝑛 ) ( 𝑦 ‘ 𝑖 )  =  ( ( ( 1  −  𝑡 )  ·  ( 𝑥 ‘ 𝑖 ) )  +  ( 𝑡  ·  ( 𝑧 ‘ 𝑖 ) ) ) ) | 
						
							| 41 | 40 1 2 3 | coprab | ⊢ { 〈 〈 𝑥 ,  𝑧 〉 ,  𝑦 〉  ∣  ∃ 𝑛  ∈  ℕ ( ( 𝑥  ∈  ( 𝔼 ‘ 𝑛 )  ∧  𝑧  ∈  ( 𝔼 ‘ 𝑛 )  ∧  𝑦  ∈  ( 𝔼 ‘ 𝑛 ) )  ∧  ∃ 𝑡  ∈  ( 0 [,] 1 ) ∀ 𝑖  ∈  ( 1 ... 𝑛 ) ( 𝑦 ‘ 𝑖 )  =  ( ( ( 1  −  𝑡 )  ·  ( 𝑥 ‘ 𝑖 ) )  +  ( 𝑡  ·  ( 𝑧 ‘ 𝑖 ) ) ) ) } | 
						
							| 42 | 41 | ccnv | ⊢ ◡ { 〈 〈 𝑥 ,  𝑧 〉 ,  𝑦 〉  ∣  ∃ 𝑛  ∈  ℕ ( ( 𝑥  ∈  ( 𝔼 ‘ 𝑛 )  ∧  𝑧  ∈  ( 𝔼 ‘ 𝑛 )  ∧  𝑦  ∈  ( 𝔼 ‘ 𝑛 ) )  ∧  ∃ 𝑡  ∈  ( 0 [,] 1 ) ∀ 𝑖  ∈  ( 1 ... 𝑛 ) ( 𝑦 ‘ 𝑖 )  =  ( ( ( 1  −  𝑡 )  ·  ( 𝑥 ‘ 𝑖 ) )  +  ( 𝑡  ·  ( 𝑧 ‘ 𝑖 ) ) ) ) } | 
						
							| 43 | 0 42 | wceq | ⊢  Btwn   =  ◡ { 〈 〈 𝑥 ,  𝑧 〉 ,  𝑦 〉  ∣  ∃ 𝑛  ∈  ℕ ( ( 𝑥  ∈  ( 𝔼 ‘ 𝑛 )  ∧  𝑧  ∈  ( 𝔼 ‘ 𝑛 )  ∧  𝑦  ∈  ( 𝔼 ‘ 𝑛 ) )  ∧  ∃ 𝑡  ∈  ( 0 [,] 1 ) ∀ 𝑖  ∈  ( 1 ... 𝑛 ) ( 𝑦 ‘ 𝑖 )  =  ( ( ( 1  −  𝑡 )  ·  ( 𝑥 ‘ 𝑖 ) )  +  ( 𝑡  ·  ( 𝑧 ‘ 𝑖 ) ) ) ) } |