| Step | Hyp | Ref | Expression | 
						
							| 1 |  | simp3 | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  𝐵  <  ( vol ‘ 𝐴 ) ) | 
						
							| 2 |  | rexr | ⊢ ( 𝐵  ∈  ℝ  →  𝐵  ∈  ℝ* ) | 
						
							| 3 | 2 | 3ad2ant2 | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  𝐵  ∈  ℝ* ) | 
						
							| 4 |  | iccssxr | ⊢ ( 0 [,] +∞ )  ⊆  ℝ* | 
						
							| 5 |  | volf | ⊢ vol : dom  vol ⟶ ( 0 [,] +∞ ) | 
						
							| 6 | 5 | ffvelcdmi | ⊢ ( 𝐴  ∈  dom  vol  →  ( vol ‘ 𝐴 )  ∈  ( 0 [,] +∞ ) ) | 
						
							| 7 | 4 6 | sselid | ⊢ ( 𝐴  ∈  dom  vol  →  ( vol ‘ 𝐴 )  ∈  ℝ* ) | 
						
							| 8 | 7 | 3ad2ant1 | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( vol ‘ 𝐴 )  ∈  ℝ* ) | 
						
							| 9 |  | xrltnle | ⊢ ( ( 𝐵  ∈  ℝ*  ∧  ( vol ‘ 𝐴 )  ∈  ℝ* )  →  ( 𝐵  <  ( vol ‘ 𝐴 )  ↔  ¬  ( vol ‘ 𝐴 )  ≤  𝐵 ) ) | 
						
							| 10 | 3 8 9 | syl2anc | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( 𝐵  <  ( vol ‘ 𝐴 )  ↔  ¬  ( vol ‘ 𝐴 )  ≤  𝐵 ) ) | 
						
							| 11 | 1 10 | mpbid | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ¬  ( vol ‘ 𝐴 )  ≤  𝐵 ) | 
						
							| 12 |  | negeq | ⊢ ( 𝑚  =  𝑛  →  - 𝑚  =  - 𝑛 ) | 
						
							| 13 |  | id | ⊢ ( 𝑚  =  𝑛  →  𝑚  =  𝑛 ) | 
						
							| 14 | 12 13 | oveq12d | ⊢ ( 𝑚  =  𝑛  →  ( - 𝑚 [,] 𝑚 )  =  ( - 𝑛 [,] 𝑛 ) ) | 
						
							| 15 | 14 | ineq2d | ⊢ ( 𝑚  =  𝑛  →  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) )  =  ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) ) | 
						
							| 16 |  | eqid | ⊢ ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) )  =  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) | 
						
							| 17 |  | ovex | ⊢ ( - 𝑛 [,] 𝑛 )  ∈  V | 
						
							| 18 | 17 | inex2 | ⊢ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) )  ∈  V | 
						
							| 19 | 15 16 18 | fvmpt | ⊢ ( 𝑛  ∈  ℕ  →  ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 )  =  ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) ) | 
						
							| 20 | 19 | iuneq2i | ⊢ ∪  𝑛  ∈  ℕ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 )  =  ∪  𝑛  ∈  ℕ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) | 
						
							| 21 |  | iunin2 | ⊢ ∪  𝑛  ∈  ℕ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) )  =  ( 𝐴  ∩  ∪  𝑛  ∈  ℕ ( - 𝑛 [,] 𝑛 ) ) | 
						
							| 22 | 20 21 | eqtri | ⊢ ∪  𝑛  ∈  ℕ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 )  =  ( 𝐴  ∩  ∪  𝑛  ∈  ℕ ( - 𝑛 [,] 𝑛 ) ) | 
						
							| 23 |  | simpl1 | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  𝐴  ∈  dom  vol ) | 
						
							| 24 |  | nnre | ⊢ ( 𝑛  ∈  ℕ  →  𝑛  ∈  ℝ ) | 
						
							| 25 | 24 | adantl | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  𝑛  ∈  ℝ ) | 
						
							| 26 | 25 | renegcld | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  - 𝑛  ∈  ℝ ) | 
						
							| 27 |  | iccmbl | ⊢ ( ( - 𝑛  ∈  ℝ  ∧  𝑛  ∈  ℝ )  →  ( - 𝑛 [,] 𝑛 )  ∈  dom  vol ) | 
						
							| 28 | 26 25 27 | syl2anc | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  ( - 𝑛 [,] 𝑛 )  ∈  dom  vol ) | 
						
							| 29 |  | inmbl | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  ( - 𝑛 [,] 𝑛 )  ∈  dom  vol )  →  ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) )  ∈  dom  vol ) | 
						
							| 30 | 23 28 29 | syl2anc | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) )  ∈  dom  vol ) | 
						
							| 31 | 15 | cbvmptv | ⊢ ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) )  =  ( 𝑛  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) ) | 
						
							| 32 | 30 31 | fmptd | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) : ℕ ⟶ dom  vol ) | 
						
							| 33 | 32 | ffnd | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) )  Fn  ℕ ) | 
						
							| 34 |  | fniunfv | ⊢ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) )  Fn  ℕ  →  ∪  𝑛  ∈  ℕ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 )  =  ∪  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ) | 
						
							| 35 | 33 34 | syl | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ∪  𝑛  ∈  ℕ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 )  =  ∪  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ) | 
						
							| 36 |  | mblss | ⊢ ( 𝐴  ∈  dom  vol  →  𝐴  ⊆  ℝ ) | 
						
							| 37 | 36 | 3ad2ant1 | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  𝐴  ⊆  ℝ ) | 
						
							| 38 | 37 | sselda | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑥  ∈  𝐴 )  →  𝑥  ∈  ℝ ) | 
						
							| 39 |  | recn | ⊢ ( 𝑥  ∈  ℝ  →  𝑥  ∈  ℂ ) | 
						
							| 40 | 39 | abscld | ⊢ ( 𝑥  ∈  ℝ  →  ( abs ‘ 𝑥 )  ∈  ℝ ) | 
						
							| 41 |  | arch | ⊢ ( ( abs ‘ 𝑥 )  ∈  ℝ  →  ∃ 𝑛  ∈  ℕ ( abs ‘ 𝑥 )  <  𝑛 ) | 
						
							| 42 | 40 41 | syl | ⊢ ( 𝑥  ∈  ℝ  →  ∃ 𝑛  ∈  ℕ ( abs ‘ 𝑥 )  <  𝑛 ) | 
						
							| 43 |  | ltle | ⊢ ( ( ( abs ‘ 𝑥 )  ∈  ℝ  ∧  𝑛  ∈  ℝ )  →  ( ( abs ‘ 𝑥 )  <  𝑛  →  ( abs ‘ 𝑥 )  ≤  𝑛 ) ) | 
						
							| 44 | 40 24 43 | syl2an | ⊢ ( ( 𝑥  ∈  ℝ  ∧  𝑛  ∈  ℕ )  →  ( ( abs ‘ 𝑥 )  <  𝑛  →  ( abs ‘ 𝑥 )  ≤  𝑛 ) ) | 
						
							| 45 |  | id | ⊢ ( ( 𝑥  ∈  ℝ  ∧  - 𝑛  ≤  𝑥  ∧  𝑥  ≤  𝑛 )  →  ( 𝑥  ∈  ℝ  ∧  - 𝑛  ≤  𝑥  ∧  𝑥  ≤  𝑛 ) ) | 
						
							| 46 | 45 | 3expib | ⊢ ( 𝑥  ∈  ℝ  →  ( ( - 𝑛  ≤  𝑥  ∧  𝑥  ≤  𝑛 )  →  ( 𝑥  ∈  ℝ  ∧  - 𝑛  ≤  𝑥  ∧  𝑥  ≤  𝑛 ) ) ) | 
						
							| 47 | 46 | adantr | ⊢ ( ( 𝑥  ∈  ℝ  ∧  𝑛  ∈  ℕ )  →  ( ( - 𝑛  ≤  𝑥  ∧  𝑥  ≤  𝑛 )  →  ( 𝑥  ∈  ℝ  ∧  - 𝑛  ≤  𝑥  ∧  𝑥  ≤  𝑛 ) ) ) | 
						
							| 48 |  | absle | ⊢ ( ( 𝑥  ∈  ℝ  ∧  𝑛  ∈  ℝ )  →  ( ( abs ‘ 𝑥 )  ≤  𝑛  ↔  ( - 𝑛  ≤  𝑥  ∧  𝑥  ≤  𝑛 ) ) ) | 
						
							| 49 | 24 48 | sylan2 | ⊢ ( ( 𝑥  ∈  ℝ  ∧  𝑛  ∈  ℕ )  →  ( ( abs ‘ 𝑥 )  ≤  𝑛  ↔  ( - 𝑛  ≤  𝑥  ∧  𝑥  ≤  𝑛 ) ) ) | 
						
							| 50 | 24 | adantl | ⊢ ( ( 𝑥  ∈  ℝ  ∧  𝑛  ∈  ℕ )  →  𝑛  ∈  ℝ ) | 
						
							| 51 | 50 | renegcld | ⊢ ( ( 𝑥  ∈  ℝ  ∧  𝑛  ∈  ℕ )  →  - 𝑛  ∈  ℝ ) | 
						
							| 52 |  | elicc2 | ⊢ ( ( - 𝑛  ∈  ℝ  ∧  𝑛  ∈  ℝ )  →  ( 𝑥  ∈  ( - 𝑛 [,] 𝑛 )  ↔  ( 𝑥  ∈  ℝ  ∧  - 𝑛  ≤  𝑥  ∧  𝑥  ≤  𝑛 ) ) ) | 
						
							| 53 | 51 50 52 | syl2anc | ⊢ ( ( 𝑥  ∈  ℝ  ∧  𝑛  ∈  ℕ )  →  ( 𝑥  ∈  ( - 𝑛 [,] 𝑛 )  ↔  ( 𝑥  ∈  ℝ  ∧  - 𝑛  ≤  𝑥  ∧  𝑥  ≤  𝑛 ) ) ) | 
						
							| 54 | 47 49 53 | 3imtr4d | ⊢ ( ( 𝑥  ∈  ℝ  ∧  𝑛  ∈  ℕ )  →  ( ( abs ‘ 𝑥 )  ≤  𝑛  →  𝑥  ∈  ( - 𝑛 [,] 𝑛 ) ) ) | 
						
							| 55 | 44 54 | syld | ⊢ ( ( 𝑥  ∈  ℝ  ∧  𝑛  ∈  ℕ )  →  ( ( abs ‘ 𝑥 )  <  𝑛  →  𝑥  ∈  ( - 𝑛 [,] 𝑛 ) ) ) | 
						
							| 56 | 55 | reximdva | ⊢ ( 𝑥  ∈  ℝ  →  ( ∃ 𝑛  ∈  ℕ ( abs ‘ 𝑥 )  <  𝑛  →  ∃ 𝑛  ∈  ℕ 𝑥  ∈  ( - 𝑛 [,] 𝑛 ) ) ) | 
						
							| 57 | 42 56 | mpd | ⊢ ( 𝑥  ∈  ℝ  →  ∃ 𝑛  ∈  ℕ 𝑥  ∈  ( - 𝑛 [,] 𝑛 ) ) | 
						
							| 58 | 38 57 | syl | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑥  ∈  𝐴 )  →  ∃ 𝑛  ∈  ℕ 𝑥  ∈  ( - 𝑛 [,] 𝑛 ) ) | 
						
							| 59 | 58 | ex | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( 𝑥  ∈  𝐴  →  ∃ 𝑛  ∈  ℕ 𝑥  ∈  ( - 𝑛 [,] 𝑛 ) ) ) | 
						
							| 60 |  | eliun | ⊢ ( 𝑥  ∈  ∪  𝑛  ∈  ℕ ( - 𝑛 [,] 𝑛 )  ↔  ∃ 𝑛  ∈  ℕ 𝑥  ∈  ( - 𝑛 [,] 𝑛 ) ) | 
						
							| 61 | 59 60 | imbitrrdi | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( 𝑥  ∈  𝐴  →  𝑥  ∈  ∪  𝑛  ∈  ℕ ( - 𝑛 [,] 𝑛 ) ) ) | 
						
							| 62 | 61 | ssrdv | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  𝐴  ⊆  ∪  𝑛  ∈  ℕ ( - 𝑛 [,] 𝑛 ) ) | 
						
							| 63 |  | dfss2 | ⊢ ( 𝐴  ⊆  ∪  𝑛  ∈  ℕ ( - 𝑛 [,] 𝑛 )  ↔  ( 𝐴  ∩  ∪  𝑛  ∈  ℕ ( - 𝑛 [,] 𝑛 ) )  =  𝐴 ) | 
						
							| 64 | 62 63 | sylib | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( 𝐴  ∩  ∪  𝑛  ∈  ℕ ( - 𝑛 [,] 𝑛 ) )  =  𝐴 ) | 
						
							| 65 | 22 35 64 | 3eqtr3a | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ∪  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) )  =  𝐴 ) | 
						
							| 66 | 65 | fveq2d | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( vol ‘ ∪  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) )  =  ( vol ‘ 𝐴 ) ) | 
						
							| 67 |  | peano2re | ⊢ ( 𝑛  ∈  ℝ  →  ( 𝑛  +  1 )  ∈  ℝ ) | 
						
							| 68 | 25 67 | syl | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  ( 𝑛  +  1 )  ∈  ℝ ) | 
						
							| 69 | 68 | renegcld | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  - ( 𝑛  +  1 )  ∈  ℝ ) | 
						
							| 70 | 25 | lep1d | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  𝑛  ≤  ( 𝑛  +  1 ) ) | 
						
							| 71 | 25 68 | lenegd | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  ( 𝑛  ≤  ( 𝑛  +  1 )  ↔  - ( 𝑛  +  1 )  ≤  - 𝑛 ) ) | 
						
							| 72 | 70 71 | mpbid | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  - ( 𝑛  +  1 )  ≤  - 𝑛 ) | 
						
							| 73 |  | iccss | ⊢ ( ( ( - ( 𝑛  +  1 )  ∈  ℝ  ∧  ( 𝑛  +  1 )  ∈  ℝ )  ∧  ( - ( 𝑛  +  1 )  ≤  - 𝑛  ∧  𝑛  ≤  ( 𝑛  +  1 ) ) )  →  ( - 𝑛 [,] 𝑛 )  ⊆  ( - ( 𝑛  +  1 ) [,] ( 𝑛  +  1 ) ) ) | 
						
							| 74 | 69 68 72 70 73 | syl22anc | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  ( - 𝑛 [,] 𝑛 )  ⊆  ( - ( 𝑛  +  1 ) [,] ( 𝑛  +  1 ) ) ) | 
						
							| 75 |  | sslin | ⊢ ( ( - 𝑛 [,] 𝑛 )  ⊆  ( - ( 𝑛  +  1 ) [,] ( 𝑛  +  1 ) )  →  ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) )  ⊆  ( 𝐴  ∩  ( - ( 𝑛  +  1 ) [,] ( 𝑛  +  1 ) ) ) ) | 
						
							| 76 | 74 75 | syl | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) )  ⊆  ( 𝐴  ∩  ( - ( 𝑛  +  1 ) [,] ( 𝑛  +  1 ) ) ) ) | 
						
							| 77 | 19 | adantl | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 )  =  ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) ) | 
						
							| 78 |  | peano2nn | ⊢ ( 𝑛  ∈  ℕ  →  ( 𝑛  +  1 )  ∈  ℕ ) | 
						
							| 79 | 78 | adantl | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  ( 𝑛  +  1 )  ∈  ℕ ) | 
						
							| 80 |  | negeq | ⊢ ( 𝑚  =  ( 𝑛  +  1 )  →  - 𝑚  =  - ( 𝑛  +  1 ) ) | 
						
							| 81 |  | id | ⊢ ( 𝑚  =  ( 𝑛  +  1 )  →  𝑚  =  ( 𝑛  +  1 ) ) | 
						
							| 82 | 80 81 | oveq12d | ⊢ ( 𝑚  =  ( 𝑛  +  1 )  →  ( - 𝑚 [,] 𝑚 )  =  ( - ( 𝑛  +  1 ) [,] ( 𝑛  +  1 ) ) ) | 
						
							| 83 | 82 | ineq2d | ⊢ ( 𝑚  =  ( 𝑛  +  1 )  →  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) )  =  ( 𝐴  ∩  ( - ( 𝑛  +  1 ) [,] ( 𝑛  +  1 ) ) ) ) | 
						
							| 84 |  | ovex | ⊢ ( - ( 𝑛  +  1 ) [,] ( 𝑛  +  1 ) )  ∈  V | 
						
							| 85 | 84 | inex2 | ⊢ ( 𝐴  ∩  ( - ( 𝑛  +  1 ) [,] ( 𝑛  +  1 ) ) )  ∈  V | 
						
							| 86 | 83 16 85 | fvmpt | ⊢ ( ( 𝑛  +  1 )  ∈  ℕ  →  ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ ( 𝑛  +  1 ) )  =  ( 𝐴  ∩  ( - ( 𝑛  +  1 ) [,] ( 𝑛  +  1 ) ) ) ) | 
						
							| 87 | 79 86 | syl | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ ( 𝑛  +  1 ) )  =  ( 𝐴  ∩  ( - ( 𝑛  +  1 ) [,] ( 𝑛  +  1 ) ) ) ) | 
						
							| 88 | 76 77 87 | 3sstr4d | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 )  ⊆  ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ ( 𝑛  +  1 ) ) ) | 
						
							| 89 | 88 | ralrimiva | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ∀ 𝑛  ∈  ℕ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 )  ⊆  ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ ( 𝑛  +  1 ) ) ) | 
						
							| 90 |  | volsup | ⊢ ( ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) : ℕ ⟶ dom  vol  ∧  ∀ 𝑛  ∈  ℕ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 )  ⊆  ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ ( 𝑛  +  1 ) ) )  →  ( vol ‘ ∪  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) )  =  sup ( ( vol  “  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ) ,  ℝ* ,   <  ) ) | 
						
							| 91 | 32 89 90 | syl2anc | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( vol ‘ ∪  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) )  =  sup ( ( vol  “  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ) ,  ℝ* ,   <  ) ) | 
						
							| 92 | 66 91 | eqtr3d | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( vol ‘ 𝐴 )  =  sup ( ( vol  “  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ) ,  ℝ* ,   <  ) ) | 
						
							| 93 | 92 | breq1d | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( ( vol ‘ 𝐴 )  ≤  𝐵  ↔  sup ( ( vol  “  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ) ,  ℝ* ,   <  )  ≤  𝐵 ) ) | 
						
							| 94 |  | imassrn | ⊢ ( vol  “  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) )  ⊆  ran  vol | 
						
							| 95 |  | frn | ⊢ ( vol : dom  vol ⟶ ( 0 [,] +∞ )  →  ran  vol  ⊆  ( 0 [,] +∞ ) ) | 
						
							| 96 | 5 95 | ax-mp | ⊢ ran  vol  ⊆  ( 0 [,] +∞ ) | 
						
							| 97 | 96 4 | sstri | ⊢ ran  vol  ⊆  ℝ* | 
						
							| 98 | 94 97 | sstri | ⊢ ( vol  “  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) )  ⊆  ℝ* | 
						
							| 99 |  | supxrleub | ⊢ ( ( ( vol  “  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) )  ⊆  ℝ*  ∧  𝐵  ∈  ℝ* )  →  ( sup ( ( vol  “  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ) ,  ℝ* ,   <  )  ≤  𝐵  ↔  ∀ 𝑛  ∈  ( vol  “  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ) 𝑛  ≤  𝐵 ) ) | 
						
							| 100 | 98 3 99 | sylancr | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( sup ( ( vol  “  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ) ,  ℝ* ,   <  )  ≤  𝐵  ↔  ∀ 𝑛  ∈  ( vol  “  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ) 𝑛  ≤  𝐵 ) ) | 
						
							| 101 |  | ffn | ⊢ ( vol : dom  vol ⟶ ( 0 [,] +∞ )  →  vol  Fn  dom  vol ) | 
						
							| 102 | 5 101 | ax-mp | ⊢ vol  Fn  dom  vol | 
						
							| 103 | 32 | frnd | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) )  ⊆  dom  vol ) | 
						
							| 104 |  | breq1 | ⊢ ( 𝑛  =  ( vol ‘ 𝑧 )  →  ( 𝑛  ≤  𝐵  ↔  ( vol ‘ 𝑧 )  ≤  𝐵 ) ) | 
						
							| 105 | 104 | ralima | ⊢ ( ( vol  Fn  dom  vol  ∧  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) )  ⊆  dom  vol )  →  ( ∀ 𝑛  ∈  ( vol  “  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ) 𝑛  ≤  𝐵  ↔  ∀ 𝑧  ∈  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ( vol ‘ 𝑧 )  ≤  𝐵 ) ) | 
						
							| 106 | 102 103 105 | sylancr | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( ∀ 𝑛  ∈  ( vol  “  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ) 𝑛  ≤  𝐵  ↔  ∀ 𝑧  ∈  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ( vol ‘ 𝑧 )  ≤  𝐵 ) ) | 
						
							| 107 |  | fveq2 | ⊢ ( 𝑧  =  ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 )  →  ( vol ‘ 𝑧 )  =  ( vol ‘ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 ) ) ) | 
						
							| 108 | 107 | breq1d | ⊢ ( 𝑧  =  ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 )  →  ( ( vol ‘ 𝑧 )  ≤  𝐵  ↔  ( vol ‘ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 ) )  ≤  𝐵 ) ) | 
						
							| 109 | 108 | ralrn | ⊢ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) )  Fn  ℕ  →  ( ∀ 𝑧  ∈  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ( vol ‘ 𝑧 )  ≤  𝐵  ↔  ∀ 𝑛  ∈  ℕ ( vol ‘ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 ) )  ≤  𝐵 ) ) | 
						
							| 110 | 33 109 | syl | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( ∀ 𝑧  ∈  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ( vol ‘ 𝑧 )  ≤  𝐵  ↔  ∀ 𝑛  ∈  ℕ ( vol ‘ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 ) )  ≤  𝐵 ) ) | 
						
							| 111 | 19 | fveq2d | ⊢ ( 𝑛  ∈  ℕ  →  ( vol ‘ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 ) )  =  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) ) ) | 
						
							| 112 | 111 | breq1d | ⊢ ( 𝑛  ∈  ℕ  →  ( ( vol ‘ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 ) )  ≤  𝐵  ↔  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ≤  𝐵 ) ) | 
						
							| 113 | 112 | ralbiia | ⊢ ( ∀ 𝑛  ∈  ℕ ( vol ‘ ( ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ‘ 𝑛 ) )  ≤  𝐵  ↔  ∀ 𝑛  ∈  ℕ ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ≤  𝐵 ) | 
						
							| 114 | 110 113 | bitrdi | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( ∀ 𝑧  ∈  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ( vol ‘ 𝑧 )  ≤  𝐵  ↔  ∀ 𝑛  ∈  ℕ ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ≤  𝐵 ) ) | 
						
							| 115 | 106 114 | bitrd | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( ∀ 𝑛  ∈  ( vol  “  ran  ( 𝑚  ∈  ℕ  ↦  ( 𝐴  ∩  ( - 𝑚 [,] 𝑚 ) ) ) ) 𝑛  ≤  𝐵  ↔  ∀ 𝑛  ∈  ℕ ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ≤  𝐵 ) ) | 
						
							| 116 | 93 100 115 | 3bitrd | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( ( vol ‘ 𝐴 )  ≤  𝐵  ↔  ∀ 𝑛  ∈  ℕ ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ≤  𝐵 ) ) | 
						
							| 117 | 11 116 | mtbid | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ¬  ∀ 𝑛  ∈  ℕ ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ≤  𝐵 ) | 
						
							| 118 |  | rexnal | ⊢ ( ∃ 𝑛  ∈  ℕ ¬  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ≤  𝐵  ↔  ¬  ∀ 𝑛  ∈  ℕ ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ≤  𝐵 ) | 
						
							| 119 | 117 118 | sylibr | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ∃ 𝑛  ∈  ℕ ¬  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ≤  𝐵 ) | 
						
							| 120 | 3 | adantr | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  𝐵  ∈  ℝ* ) | 
						
							| 121 | 5 | ffvelcdmi | ⊢ ( ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) )  ∈  dom  vol  →  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ∈  ( 0 [,] +∞ ) ) | 
						
							| 122 | 4 121 | sselid | ⊢ ( ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) )  ∈  dom  vol  →  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ∈  ℝ* ) | 
						
							| 123 | 30 122 | syl | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ∈  ℝ* ) | 
						
							| 124 |  | xrltnle | ⊢ ( ( 𝐵  ∈  ℝ*  ∧  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ∈  ℝ* )  →  ( 𝐵  <  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ↔  ¬  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ≤  𝐵 ) ) | 
						
							| 125 | 120 123 124 | syl2anc | ⊢ ( ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  ∧  𝑛  ∈  ℕ )  →  ( 𝐵  <  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ↔  ¬  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ≤  𝐵 ) ) | 
						
							| 126 | 125 | rexbidva | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ( ∃ 𝑛  ∈  ℕ 𝐵  <  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ↔  ∃ 𝑛  ∈  ℕ ¬  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) )  ≤  𝐵 ) ) | 
						
							| 127 | 119 126 | mpbird | ⊢ ( ( 𝐴  ∈  dom  vol  ∧  𝐵  ∈  ℝ  ∧  𝐵  <  ( vol ‘ 𝐴 ) )  →  ∃ 𝑛  ∈  ℕ 𝐵  <  ( vol ‘ ( 𝐴  ∩  ( - 𝑛 [,] 𝑛 ) ) ) ) |