| Step | Hyp | Ref | Expression | 
						
							| 1 |  | itgadd.1 | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  𝐵  ∈  𝑉 ) | 
						
							| 2 |  | itgadd.2 | ⊢ ( 𝜑  →  ( 𝑥  ∈  𝐴  ↦  𝐵 )  ∈  𝐿1 ) | 
						
							| 3 |  | itgadd.3 | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  𝐶  ∈  𝑉 ) | 
						
							| 4 |  | itgadd.4 | ⊢ ( 𝜑  →  ( 𝑥  ∈  𝐴  ↦  𝐶 )  ∈  𝐿1 ) | 
						
							| 5 |  | itgadd.5 | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  𝐵  ∈  ℝ ) | 
						
							| 6 |  | itgadd.6 | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  𝐶  ∈  ℝ ) | 
						
							| 7 |  | max0sub | ⊢ ( 𝐵  ∈  ℝ  →  ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  −  if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 ) )  =  𝐵 ) | 
						
							| 8 | 5 7 | syl | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  −  if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 ) )  =  𝐵 ) | 
						
							| 9 |  | max0sub | ⊢ ( 𝐶  ∈  ℝ  →  ( if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  −  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  =  𝐶 ) | 
						
							| 10 | 6 9 | syl | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  ( if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  −  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  =  𝐶 ) | 
						
							| 11 | 8 10 | oveq12d | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  ( ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  −  if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 ) )  +  ( if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  −  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) ) )  =  ( 𝐵  +  𝐶 ) ) | 
						
							| 12 |  | 0re | ⊢ 0  ∈  ℝ | 
						
							| 13 |  | ifcl | ⊢ ( ( 𝐵  ∈  ℝ  ∧  0  ∈  ℝ )  →  if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  ∈  ℝ ) | 
						
							| 14 | 5 12 13 | sylancl | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  ∈  ℝ ) | 
						
							| 15 | 14 | recnd | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  ∈  ℂ ) | 
						
							| 16 |  | ifcl | ⊢ ( ( 𝐶  ∈  ℝ  ∧  0  ∈  ℝ )  →  if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  ∈  ℝ ) | 
						
							| 17 | 6 12 16 | sylancl | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  ∈  ℝ ) | 
						
							| 18 | 17 | recnd | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  ∈  ℂ ) | 
						
							| 19 | 5 | renegcld | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  - 𝐵  ∈  ℝ ) | 
						
							| 20 |  | ifcl | ⊢ ( ( - 𝐵  ∈  ℝ  ∧  0  ∈  ℝ )  →  if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  ∈  ℝ ) | 
						
							| 21 | 19 12 20 | sylancl | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  ∈  ℝ ) | 
						
							| 22 | 21 | recnd | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  ∈  ℂ ) | 
						
							| 23 | 6 | renegcld | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  - 𝐶  ∈  ℝ ) | 
						
							| 24 |  | ifcl | ⊢ ( ( - 𝐶  ∈  ℝ  ∧  0  ∈  ℝ )  →  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 )  ∈  ℝ ) | 
						
							| 25 | 23 12 24 | sylancl | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 )  ∈  ℝ ) | 
						
							| 26 | 25 | recnd | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 )  ∈  ℂ ) | 
						
							| 27 | 15 18 22 26 | addsub4d | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  ( ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  −  ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) ) )  =  ( ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  −  if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 ) )  +  ( if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  −  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) ) ) ) | 
						
							| 28 | 5 6 | readdcld | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  ( 𝐵  +  𝐶 )  ∈  ℝ ) | 
						
							| 29 |  | max0sub | ⊢ ( ( 𝐵  +  𝐶 )  ∈  ℝ  →  ( if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  −  if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 ) )  =  ( 𝐵  +  𝐶 ) ) | 
						
							| 30 | 28 29 | syl | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  ( if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  −  if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 ) )  =  ( 𝐵  +  𝐶 ) ) | 
						
							| 31 | 11 27 30 | 3eqtr4rd | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  ( if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  −  if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 ) )  =  ( ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  −  ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) ) ) ) | 
						
							| 32 | 28 | renegcld | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  - ( 𝐵  +  𝐶 )  ∈  ℝ ) | 
						
							| 33 |  | ifcl | ⊢ ( ( - ( 𝐵  +  𝐶 )  ∈  ℝ  ∧  0  ∈  ℝ )  →  if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  ∈  ℝ ) | 
						
							| 34 | 32 12 33 | sylancl | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  ∈  ℝ ) | 
						
							| 35 | 34 | recnd | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  ∈  ℂ ) | 
						
							| 36 | 15 18 | addcld | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  ∈  ℂ ) | 
						
							| 37 |  | ifcl | ⊢ ( ( ( 𝐵  +  𝐶 )  ∈  ℝ  ∧  0  ∈  ℝ )  →  if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  ∈  ℝ ) | 
						
							| 38 | 28 12 37 | sylancl | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  ∈  ℝ ) | 
						
							| 39 | 38 | recnd | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  ∈  ℂ ) | 
						
							| 40 | 22 26 | addcld | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  ∈  ℂ ) | 
						
							| 41 | 35 36 39 40 | addsubeq4d | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  ( ( if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  +  ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) ) )  =  ( if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  +  ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) ) )  ↔  ( if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  −  if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 ) )  =  ( ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  −  ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) ) ) ) ) | 
						
							| 42 | 31 41 | mpbird | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  ( if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  +  ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) ) )  =  ( if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  +  ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) ) ) ) | 
						
							| 43 | 42 | itgeq2dv | ⊢ ( 𝜑  →  ∫ 𝐴 ( if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  +  ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) ) )  d 𝑥  =  ∫ 𝐴 ( if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  +  ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) ) )  d 𝑥 ) | 
						
							| 44 | 1 2 3 4 | ibladd | ⊢ ( 𝜑  →  ( 𝑥  ∈  𝐴  ↦  ( 𝐵  +  𝐶 ) )  ∈  𝐿1 ) | 
						
							| 45 | 28 | iblre | ⊢ ( 𝜑  →  ( ( 𝑥  ∈  𝐴  ↦  ( 𝐵  +  𝐶 ) )  ∈  𝐿1  ↔  ( ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 ) )  ∈  𝐿1  ∧  ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 ) )  ∈  𝐿1 ) ) ) | 
						
							| 46 | 44 45 | mpbid | ⊢ ( 𝜑  →  ( ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 ) )  ∈  𝐿1  ∧  ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 ) )  ∈  𝐿1 ) ) | 
						
							| 47 | 46 | simprd | ⊢ ( 𝜑  →  ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 ) )  ∈  𝐿1 ) | 
						
							| 48 | 14 17 | readdcld | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  ∈  ℝ ) | 
						
							| 49 | 5 | iblre | ⊢ ( 𝜑  →  ( ( 𝑥  ∈  𝐴  ↦  𝐵 )  ∈  𝐿1  ↔  ( ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  𝐵 ,  𝐵 ,  0 ) )  ∈  𝐿1  ∧  ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 ) )  ∈  𝐿1 ) ) ) | 
						
							| 50 | 2 49 | mpbid | ⊢ ( 𝜑  →  ( ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  𝐵 ,  𝐵 ,  0 ) )  ∈  𝐿1  ∧  ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 ) )  ∈  𝐿1 ) ) | 
						
							| 51 | 50 | simpld | ⊢ ( 𝜑  →  ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  𝐵 ,  𝐵 ,  0 ) )  ∈  𝐿1 ) | 
						
							| 52 | 6 | iblre | ⊢ ( 𝜑  →  ( ( 𝑥  ∈  𝐴  ↦  𝐶 )  ∈  𝐿1  ↔  ( ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  ∈  𝐿1  ∧  ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  ∈  𝐿1 ) ) ) | 
						
							| 53 | 4 52 | mpbid | ⊢ ( 𝜑  →  ( ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  ∈  𝐿1  ∧  ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  ∈  𝐿1 ) ) | 
						
							| 54 | 53 | simpld | ⊢ ( 𝜑  →  ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  ∈  𝐿1 ) | 
						
							| 55 | 14 51 17 54 | ibladd | ⊢ ( 𝜑  →  ( 𝑥  ∈  𝐴  ↦  ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) ) )  ∈  𝐿1 ) | 
						
							| 56 |  | max1 | ⊢ ( ( 0  ∈  ℝ  ∧  - ( 𝐵  +  𝐶 )  ∈  ℝ )  →  0  ≤  if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 ) ) | 
						
							| 57 | 12 32 56 | sylancr | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  0  ≤  if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 ) ) | 
						
							| 58 |  | max1 | ⊢ ( ( 0  ∈  ℝ  ∧  𝐵  ∈  ℝ )  →  0  ≤  if ( 0  ≤  𝐵 ,  𝐵 ,  0 ) ) | 
						
							| 59 | 12 5 58 | sylancr | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  0  ≤  if ( 0  ≤  𝐵 ,  𝐵 ,  0 ) ) | 
						
							| 60 |  | max1 | ⊢ ( ( 0  ∈  ℝ  ∧  𝐶  ∈  ℝ )  →  0  ≤  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) ) | 
						
							| 61 | 12 6 60 | sylancr | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  0  ≤  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) ) | 
						
							| 62 | 14 17 59 61 | addge0d | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  0  ≤  ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) ) ) | 
						
							| 63 | 34 47 48 55 34 48 57 62 | itgaddlem1 | ⊢ ( 𝜑  →  ∫ 𝐴 ( if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  +  ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) ) )  d 𝑥  =  ( ∫ 𝐴 if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥  +  ∫ 𝐴 ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  d 𝑥 ) ) | 
						
							| 64 | 46 | simpld | ⊢ ( 𝜑  →  ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 ) )  ∈  𝐿1 ) | 
						
							| 65 | 21 25 | readdcld | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  ∈  ℝ ) | 
						
							| 66 | 50 | simprd | ⊢ ( 𝜑  →  ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 ) )  ∈  𝐿1 ) | 
						
							| 67 | 53 | simprd | ⊢ ( 𝜑  →  ( 𝑥  ∈  𝐴  ↦  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  ∈  𝐿1 ) | 
						
							| 68 | 21 66 25 67 | ibladd | ⊢ ( 𝜑  →  ( 𝑥  ∈  𝐴  ↦  ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) ) )  ∈  𝐿1 ) | 
						
							| 69 |  | max1 | ⊢ ( ( 0  ∈  ℝ  ∧  ( 𝐵  +  𝐶 )  ∈  ℝ )  →  0  ≤  if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 ) ) | 
						
							| 70 | 12 28 69 | sylancr | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  0  ≤  if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 ) ) | 
						
							| 71 |  | max1 | ⊢ ( ( 0  ∈  ℝ  ∧  - 𝐵  ∈  ℝ )  →  0  ≤  if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 ) ) | 
						
							| 72 | 12 19 71 | sylancr | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  0  ≤  if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 ) ) | 
						
							| 73 |  | max1 | ⊢ ( ( 0  ∈  ℝ  ∧  - 𝐶  ∈  ℝ )  →  0  ≤  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) ) | 
						
							| 74 | 12 23 73 | sylancr | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  0  ≤  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) ) | 
						
							| 75 | 21 25 72 74 | addge0d | ⊢ ( ( 𝜑  ∧  𝑥  ∈  𝐴 )  →  0  ≤  ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) ) ) | 
						
							| 76 | 38 64 65 68 38 65 70 75 | itgaddlem1 | ⊢ ( 𝜑  →  ∫ 𝐴 ( if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  +  ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) ) )  d 𝑥  =  ( ∫ 𝐴 if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥  +  ∫ 𝐴 ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  d 𝑥 ) ) | 
						
							| 77 | 43 63 76 | 3eqtr3d | ⊢ ( 𝜑  →  ( ∫ 𝐴 if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥  +  ∫ 𝐴 ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  d 𝑥 )  =  ( ∫ 𝐴 if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥  +  ∫ 𝐴 ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  d 𝑥 ) ) | 
						
							| 78 | 34 47 | itgcl | ⊢ ( 𝜑  →  ∫ 𝐴 if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥  ∈  ℂ ) | 
						
							| 79 | 14 51 17 54 14 17 59 61 | itgaddlem1 | ⊢ ( 𝜑  →  ∫ 𝐴 ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  d 𝑥  =  ( ∫ 𝐴 if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  d 𝑥  +  ∫ 𝐴 if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  d 𝑥 ) ) | 
						
							| 80 | 14 51 | itgcl | ⊢ ( 𝜑  →  ∫ 𝐴 if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  d 𝑥  ∈  ℂ ) | 
						
							| 81 | 17 54 | itgcl | ⊢ ( 𝜑  →  ∫ 𝐴 if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  d 𝑥  ∈  ℂ ) | 
						
							| 82 | 80 81 | addcld | ⊢ ( 𝜑  →  ( ∫ 𝐴 if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  d 𝑥  +  ∫ 𝐴 if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  d 𝑥 )  ∈  ℂ ) | 
						
							| 83 | 79 82 | eqeltrd | ⊢ ( 𝜑  →  ∫ 𝐴 ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  d 𝑥  ∈  ℂ ) | 
						
							| 84 | 38 64 | itgcl | ⊢ ( 𝜑  →  ∫ 𝐴 if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥  ∈  ℂ ) | 
						
							| 85 | 21 66 25 67 21 25 72 74 | itgaddlem1 | ⊢ ( 𝜑  →  ∫ 𝐴 ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  d 𝑥  =  ( ∫ 𝐴 if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  d 𝑥  +  ∫ 𝐴 if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 )  d 𝑥 ) ) | 
						
							| 86 | 21 66 | itgcl | ⊢ ( 𝜑  →  ∫ 𝐴 if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  d 𝑥  ∈  ℂ ) | 
						
							| 87 | 25 67 | itgcl | ⊢ ( 𝜑  →  ∫ 𝐴 if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 )  d 𝑥  ∈  ℂ ) | 
						
							| 88 | 86 87 | addcld | ⊢ ( 𝜑  →  ( ∫ 𝐴 if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  d 𝑥  +  ∫ 𝐴 if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 )  d 𝑥 )  ∈  ℂ ) | 
						
							| 89 | 85 88 | eqeltrd | ⊢ ( 𝜑  →  ∫ 𝐴 ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  d 𝑥  ∈  ℂ ) | 
						
							| 90 | 78 83 84 89 | addsubeq4d | ⊢ ( 𝜑  →  ( ( ∫ 𝐴 if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥  +  ∫ 𝐴 ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  d 𝑥 )  =  ( ∫ 𝐴 if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥  +  ∫ 𝐴 ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  d 𝑥 )  ↔  ( ∫ 𝐴 if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥  −  ∫ 𝐴 if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥 )  =  ( ∫ 𝐴 ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  d 𝑥  −  ∫ 𝐴 ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  d 𝑥 ) ) ) | 
						
							| 91 | 77 90 | mpbid | ⊢ ( 𝜑  →  ( ∫ 𝐴 if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥  −  ∫ 𝐴 if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥 )  =  ( ∫ 𝐴 ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  d 𝑥  −  ∫ 𝐴 ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  d 𝑥 ) ) | 
						
							| 92 | 79 85 | oveq12d | ⊢ ( 𝜑  →  ( ∫ 𝐴 ( if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  +  if ( 0  ≤  𝐶 ,  𝐶 ,  0 ) )  d 𝑥  −  ∫ 𝐴 ( if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  +  if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 ) )  d 𝑥 )  =  ( ( ∫ 𝐴 if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  d 𝑥  +  ∫ 𝐴 if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  d 𝑥 )  −  ( ∫ 𝐴 if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  d 𝑥  +  ∫ 𝐴 if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 )  d 𝑥 ) ) ) | 
						
							| 93 | 80 81 86 87 | addsub4d | ⊢ ( 𝜑  →  ( ( ∫ 𝐴 if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  d 𝑥  +  ∫ 𝐴 if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  d 𝑥 )  −  ( ∫ 𝐴 if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  d 𝑥  +  ∫ 𝐴 if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 )  d 𝑥 ) )  =  ( ( ∫ 𝐴 if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  d 𝑥  −  ∫ 𝐴 if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  d 𝑥 )  +  ( ∫ 𝐴 if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  d 𝑥  −  ∫ 𝐴 if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 )  d 𝑥 ) ) ) | 
						
							| 94 | 91 92 93 | 3eqtrd | ⊢ ( 𝜑  →  ( ∫ 𝐴 if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥  −  ∫ 𝐴 if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥 )  =  ( ( ∫ 𝐴 if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  d 𝑥  −  ∫ 𝐴 if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  d 𝑥 )  +  ( ∫ 𝐴 if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  d 𝑥  −  ∫ 𝐴 if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 )  d 𝑥 ) ) ) | 
						
							| 95 | 28 44 | itgreval | ⊢ ( 𝜑  →  ∫ 𝐴 ( 𝐵  +  𝐶 )  d 𝑥  =  ( ∫ 𝐴 if ( 0  ≤  ( 𝐵  +  𝐶 ) ,  ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥  −  ∫ 𝐴 if ( 0  ≤  - ( 𝐵  +  𝐶 ) ,  - ( 𝐵  +  𝐶 ) ,  0 )  d 𝑥 ) ) | 
						
							| 96 | 5 2 | itgreval | ⊢ ( 𝜑  →  ∫ 𝐴 𝐵  d 𝑥  =  ( ∫ 𝐴 if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  d 𝑥  −  ∫ 𝐴 if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  d 𝑥 ) ) | 
						
							| 97 | 6 4 | itgreval | ⊢ ( 𝜑  →  ∫ 𝐴 𝐶  d 𝑥  =  ( ∫ 𝐴 if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  d 𝑥  −  ∫ 𝐴 if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 )  d 𝑥 ) ) | 
						
							| 98 | 96 97 | oveq12d | ⊢ ( 𝜑  →  ( ∫ 𝐴 𝐵  d 𝑥  +  ∫ 𝐴 𝐶  d 𝑥 )  =  ( ( ∫ 𝐴 if ( 0  ≤  𝐵 ,  𝐵 ,  0 )  d 𝑥  −  ∫ 𝐴 if ( 0  ≤  - 𝐵 ,  - 𝐵 ,  0 )  d 𝑥 )  +  ( ∫ 𝐴 if ( 0  ≤  𝐶 ,  𝐶 ,  0 )  d 𝑥  −  ∫ 𝐴 if ( 0  ≤  - 𝐶 ,  - 𝐶 ,  0 )  d 𝑥 ) ) ) | 
						
							| 99 | 94 95 98 | 3eqtr4d | ⊢ ( 𝜑  →  ∫ 𝐴 ( 𝐵  +  𝐶 )  d 𝑥  =  ( ∫ 𝐴 𝐵  d 𝑥  +  ∫ 𝐴 𝐶  d 𝑥 ) ) |