Metamath Proof Explorer


Theorem vonicclem1

Description: The sequence of the measures of the half-open intervals converges to the measure of their intersection. (Contributed by Glauco Siliprandi, 8-Apr-2021)

Ref Expression
Hypotheses vonicclem1.x ( 𝜑𝑋 ∈ Fin )
vonicclem1.a ( 𝜑𝐴 : 𝑋 ⟶ ℝ )
vonicclem1.b ( 𝜑𝐵 : 𝑋 ⟶ ℝ )
vonicclem1.u ( 𝜑𝑋 ≠ ∅ )
vonicclem1.t ( ( 𝜑𝑘𝑋 ) → ( 𝐴𝑘 ) ≤ ( 𝐵𝑘 ) )
vonicclem1.c 𝐶 = ( 𝑛 ∈ ℕ ↦ ( 𝑘𝑋 ↦ ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) ) )
vonicclem1.d 𝐷 = ( 𝑛 ∈ ℕ ↦ X 𝑘𝑋 ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) )
vonicclem1.s 𝑆 = ( 𝑛 ∈ ℕ ↦ ( ( voln ‘ 𝑋 ) ‘ ( 𝐷𝑛 ) ) )
Assertion vonicclem1 ( 𝜑𝑆 ⇝ ∏ 𝑘𝑋 ( ( 𝐵𝑘 ) − ( 𝐴𝑘 ) ) )

Proof

Step Hyp Ref Expression
1 vonicclem1.x ( 𝜑𝑋 ∈ Fin )
2 vonicclem1.a ( 𝜑𝐴 : 𝑋 ⟶ ℝ )
3 vonicclem1.b ( 𝜑𝐵 : 𝑋 ⟶ ℝ )
4 vonicclem1.u ( 𝜑𝑋 ≠ ∅ )
5 vonicclem1.t ( ( 𝜑𝑘𝑋 ) → ( 𝐴𝑘 ) ≤ ( 𝐵𝑘 ) )
6 vonicclem1.c 𝐶 = ( 𝑛 ∈ ℕ ↦ ( 𝑘𝑋 ↦ ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) ) )
7 vonicclem1.d 𝐷 = ( 𝑛 ∈ ℕ ↦ X 𝑘𝑋 ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) )
8 vonicclem1.s 𝑆 = ( 𝑛 ∈ ℕ ↦ ( ( voln ‘ 𝑋 ) ‘ ( 𝐷𝑛 ) ) )
9 8 a1i ( 𝜑𝑆 = ( 𝑛 ∈ ℕ ↦ ( ( voln ‘ 𝑋 ) ‘ ( 𝐷𝑛 ) ) ) )
10 simpr ( ( 𝜑𝑛 ∈ ℕ ) → 𝑛 ∈ ℕ )
11 7 a1i ( 𝜑𝐷 = ( 𝑛 ∈ ℕ ↦ X 𝑘𝑋 ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) ) )
12 1 adantr ( ( 𝜑𝑛 ∈ ℕ ) → 𝑋 ∈ Fin )
13 eqid dom ( voln ‘ 𝑋 ) = dom ( voln ‘ 𝑋 )
14 2 adantr ( ( 𝜑𝑛 ∈ ℕ ) → 𝐴 : 𝑋 ⟶ ℝ )
15 3 ffvelrnda ( ( 𝜑𝑘𝑋 ) → ( 𝐵𝑘 ) ∈ ℝ )
16 15 adantlr ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( 𝐵𝑘 ) ∈ ℝ )
17 nnrecre ( 𝑛 ∈ ℕ → ( 1 / 𝑛 ) ∈ ℝ )
18 17 ad2antlr ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( 1 / 𝑛 ) ∈ ℝ )
19 16 18 readdcld ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) ∈ ℝ )
20 19 fmpttd ( ( 𝜑𝑛 ∈ ℕ ) → ( 𝑘𝑋 ↦ ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) ) : 𝑋 ⟶ ℝ )
21 6 a1i ( 𝜑𝐶 = ( 𝑛 ∈ ℕ ↦ ( 𝑘𝑋 ↦ ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) ) ) )
22 1 mptexd ( 𝜑 → ( 𝑘𝑋 ↦ ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) ) ∈ V )
23 22 adantr ( ( 𝜑𝑛 ∈ ℕ ) → ( 𝑘𝑋 ↦ ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) ) ∈ V )
24 21 23 fvmpt2d ( ( 𝜑𝑛 ∈ ℕ ) → ( 𝐶𝑛 ) = ( 𝑘𝑋 ↦ ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) ) )
25 24 feq1d ( ( 𝜑𝑛 ∈ ℕ ) → ( ( 𝐶𝑛 ) : 𝑋 ⟶ ℝ ↔ ( 𝑘𝑋 ↦ ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) ) : 𝑋 ⟶ ℝ ) )
26 20 25 mpbird ( ( 𝜑𝑛 ∈ ℕ ) → ( 𝐶𝑛 ) : 𝑋 ⟶ ℝ )
27 12 13 14 26 hoimbl ( ( 𝜑𝑛 ∈ ℕ ) → X 𝑘𝑋 ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) ∈ dom ( voln ‘ 𝑋 ) )
28 27 elexd ( ( 𝜑𝑛 ∈ ℕ ) → X 𝑘𝑋 ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) ∈ V )
29 11 28 fvmpt2d ( ( 𝜑𝑛 ∈ ℕ ) → ( 𝐷𝑛 ) = X 𝑘𝑋 ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) )
30 10 29 syldan ( ( 𝜑𝑛 ∈ ℕ ) → ( 𝐷𝑛 ) = X 𝑘𝑋 ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) )
31 30 fveq2d ( ( 𝜑𝑛 ∈ ℕ ) → ( ( voln ‘ 𝑋 ) ‘ ( 𝐷𝑛 ) ) = ( ( voln ‘ 𝑋 ) ‘ X 𝑘𝑋 ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) ) )
32 4 adantr ( ( 𝜑𝑛 ∈ ℕ ) → 𝑋 ≠ ∅ )
33 10 26 syldan ( ( 𝜑𝑛 ∈ ℕ ) → ( 𝐶𝑛 ) : 𝑋 ⟶ ℝ )
34 eqid X 𝑘𝑋 ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) = X 𝑘𝑋 ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) )
35 12 32 14 33 34 vonn0hoi ( ( 𝜑𝑛 ∈ ℕ ) → ( ( voln ‘ 𝑋 ) ‘ X 𝑘𝑋 ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) ) = ∏ 𝑘𝑋 ( vol ‘ ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) ) )
36 14 ffvelrnda ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( 𝐴𝑘 ) ∈ ℝ )
37 10 36 syldanl ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( 𝐴𝑘 ) ∈ ℝ )
38 33 ffvelrnda ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( ( 𝐶𝑛 ) ‘ 𝑘 ) ∈ ℝ )
39 volico ( ( ( 𝐴𝑘 ) ∈ ℝ ∧ ( ( 𝐶𝑛 ) ‘ 𝑘 ) ∈ ℝ ) → ( vol ‘ ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) ) = if ( ( 𝐴𝑘 ) < ( ( 𝐶𝑛 ) ‘ 𝑘 ) , ( ( ( 𝐶𝑛 ) ‘ 𝑘 ) − ( 𝐴𝑘 ) ) , 0 ) )
40 37 38 39 syl2anc ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( vol ‘ ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) ) = if ( ( 𝐴𝑘 ) < ( ( 𝐶𝑛 ) ‘ 𝑘 ) , ( ( ( 𝐶𝑛 ) ‘ 𝑘 ) − ( 𝐴𝑘 ) ) , 0 ) )
41 10 16 syldanl ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( 𝐵𝑘 ) ∈ ℝ )
42 5 adantlr ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( 𝐴𝑘 ) ≤ ( 𝐵𝑘 ) )
43 nnrp ( 𝑛 ∈ ℕ → 𝑛 ∈ ℝ+ )
44 43 rpreccld ( 𝑛 ∈ ℕ → ( 1 / 𝑛 ) ∈ ℝ+ )
45 44 ad2antlr ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( 1 / 𝑛 ) ∈ ℝ+ )
46 41 45 ltaddrpd ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( 𝐵𝑘 ) < ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) )
47 19 elexd ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) ∈ V )
48 24 47 fvmpt2d ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( ( 𝐶𝑛 ) ‘ 𝑘 ) = ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) )
49 10 48 syldanl ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( ( 𝐶𝑛 ) ‘ 𝑘 ) = ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) )
50 46 49 breqtrrd ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( 𝐵𝑘 ) < ( ( 𝐶𝑛 ) ‘ 𝑘 ) )
51 37 41 38 42 50 lelttrd ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( 𝐴𝑘 ) < ( ( 𝐶𝑛 ) ‘ 𝑘 ) )
52 51 iftrued ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → if ( ( 𝐴𝑘 ) < ( ( 𝐶𝑛 ) ‘ 𝑘 ) , ( ( ( 𝐶𝑛 ) ‘ 𝑘 ) − ( 𝐴𝑘 ) ) , 0 ) = ( ( ( 𝐶𝑛 ) ‘ 𝑘 ) − ( 𝐴𝑘 ) ) )
53 40 52 eqtrd ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( vol ‘ ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) ) = ( ( ( 𝐶𝑛 ) ‘ 𝑘 ) − ( 𝐴𝑘 ) ) )
54 53 prodeq2dv ( ( 𝜑𝑛 ∈ ℕ ) → ∏ 𝑘𝑋 ( vol ‘ ( ( 𝐴𝑘 ) [,) ( ( 𝐶𝑛 ) ‘ 𝑘 ) ) ) = ∏ 𝑘𝑋 ( ( ( 𝐶𝑛 ) ‘ 𝑘 ) − ( 𝐴𝑘 ) ) )
55 31 35 54 3eqtrd ( ( 𝜑𝑛 ∈ ℕ ) → ( ( voln ‘ 𝑋 ) ‘ ( 𝐷𝑛 ) ) = ∏ 𝑘𝑋 ( ( ( 𝐶𝑛 ) ‘ 𝑘 ) − ( 𝐴𝑘 ) ) )
56 48 oveq1d ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( ( ( 𝐶𝑛 ) ‘ 𝑘 ) − ( 𝐴𝑘 ) ) = ( ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) − ( 𝐴𝑘 ) ) )
57 16 recnd ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( 𝐵𝑘 ) ∈ ℂ )
58 18 recnd ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( 1 / 𝑛 ) ∈ ℂ )
59 36 recnd ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( 𝐴𝑘 ) ∈ ℂ )
60 57 58 59 addsubd ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( ( ( 𝐵𝑘 ) + ( 1 / 𝑛 ) ) − ( 𝐴𝑘 ) ) = ( ( ( 𝐵𝑘 ) − ( 𝐴𝑘 ) ) + ( 1 / 𝑛 ) ) )
61 56 60 eqtrd ( ( ( 𝜑𝑛 ∈ ℕ ) ∧ 𝑘𝑋 ) → ( ( ( 𝐶𝑛 ) ‘ 𝑘 ) − ( 𝐴𝑘 ) ) = ( ( ( 𝐵𝑘 ) − ( 𝐴𝑘 ) ) + ( 1 / 𝑛 ) ) )
62 61 prodeq2dv ( ( 𝜑𝑛 ∈ ℕ ) → ∏ 𝑘𝑋 ( ( ( 𝐶𝑛 ) ‘ 𝑘 ) − ( 𝐴𝑘 ) ) = ∏ 𝑘𝑋 ( ( ( 𝐵𝑘 ) − ( 𝐴𝑘 ) ) + ( 1 / 𝑛 ) ) )
63 55 62 eqtrd ( ( 𝜑𝑛 ∈ ℕ ) → ( ( voln ‘ 𝑋 ) ‘ ( 𝐷𝑛 ) ) = ∏ 𝑘𝑋 ( ( ( 𝐵𝑘 ) − ( 𝐴𝑘 ) ) + ( 1 / 𝑛 ) ) )
64 63 mpteq2dva ( 𝜑 → ( 𝑛 ∈ ℕ ↦ ( ( voln ‘ 𝑋 ) ‘ ( 𝐷𝑛 ) ) ) = ( 𝑛 ∈ ℕ ↦ ∏ 𝑘𝑋 ( ( ( 𝐵𝑘 ) − ( 𝐴𝑘 ) ) + ( 1 / 𝑛 ) ) ) )
65 9 64 eqtrd ( 𝜑𝑆 = ( 𝑛 ∈ ℕ ↦ ∏ 𝑘𝑋 ( ( ( 𝐵𝑘 ) − ( 𝐴𝑘 ) ) + ( 1 / 𝑛 ) ) ) )
66 nfv 𝑘 𝜑
67 2 ffvelrnda ( ( 𝜑𝑘𝑋 ) → ( 𝐴𝑘 ) ∈ ℝ )
68 15 67 resubcld ( ( 𝜑𝑘𝑋 ) → ( ( 𝐵𝑘 ) − ( 𝐴𝑘 ) ) ∈ ℝ )
69 68 recnd ( ( 𝜑𝑘𝑋 ) → ( ( 𝐵𝑘 ) − ( 𝐴𝑘 ) ) ∈ ℂ )
70 eqid ( 𝑛 ∈ ℕ ↦ ∏ 𝑘𝑋 ( ( ( 𝐵𝑘 ) − ( 𝐴𝑘 ) ) + ( 1 / 𝑛 ) ) ) = ( 𝑛 ∈ ℕ ↦ ∏ 𝑘𝑋 ( ( ( 𝐵𝑘 ) − ( 𝐴𝑘 ) ) + ( 1 / 𝑛 ) ) )
71 66 1 69 70 fprodaddrecnncnv ( 𝜑 → ( 𝑛 ∈ ℕ ↦ ∏ 𝑘𝑋 ( ( ( 𝐵𝑘 ) − ( 𝐴𝑘 ) ) + ( 1 / 𝑛 ) ) ) ⇝ ∏ 𝑘𝑋 ( ( 𝐵𝑘 ) − ( 𝐴𝑘 ) ) )
72 65 71 eqbrtrd ( 𝜑𝑆 ⇝ ∏ 𝑘𝑋 ( ( 𝐵𝑘 ) − ( 𝐴𝑘 ) ) )