Metamath Proof Explorer


Theorem dvgrat

Description: Ratio test for divergence of a complex infinite series. See e.g. remark "if ( abs( ( a( n + 1 ) ) / ( an ) ) ) >_ 1 for all large n..." in https://en.wikipedia.org/wiki/Ratio_test#The_test . (Contributed by Steve Rodriguez, 28-Feb-2020)

Ref Expression
Hypotheses dvgrat.z 𝑍 = ( ℤ𝑀 )
dvgrat.w 𝑊 = ( ℤ𝑁 )
dvgrat.n ( 𝜑𝑁𝑍 )
dvgrat.f ( 𝜑𝐹𝑉 )
dvgrat.c ( ( 𝜑𝑘𝑍 ) → ( 𝐹𝑘 ) ∈ ℂ )
dvgrat.n0 ( ( 𝜑𝑘𝑊 ) → ( 𝐹𝑘 ) ≠ 0 )
dvgrat.le ( ( 𝜑𝑘𝑊 ) → ( abs ‘ ( 𝐹𝑘 ) ) ≤ ( abs ‘ ( 𝐹 ‘ ( 𝑘 + 1 ) ) ) )
Assertion dvgrat ( 𝜑 → seq 𝑀 ( + , 𝐹 ) ∉ dom ⇝ )

Proof

Step Hyp Ref Expression
1 dvgrat.z 𝑍 = ( ℤ𝑀 )
2 dvgrat.w 𝑊 = ( ℤ𝑁 )
3 dvgrat.n ( 𝜑𝑁𝑍 )
4 dvgrat.f ( 𝜑𝐹𝑉 )
5 dvgrat.c ( ( 𝜑𝑘𝑍 ) → ( 𝐹𝑘 ) ∈ ℂ )
6 dvgrat.n0 ( ( 𝜑𝑘𝑊 ) → ( 𝐹𝑘 ) ≠ 0 )
7 dvgrat.le ( ( 𝜑𝑘𝑊 ) → ( abs ‘ ( 𝐹𝑘 ) ) ≤ ( abs ‘ ( 𝐹 ‘ ( 𝑘 + 1 ) ) ) )
8 3 1 eleqtrdi ( 𝜑𝑁 ∈ ( ℤ𝑀 ) )
9 eluzelz ( 𝑁 ∈ ( ℤ𝑀 ) → 𝑁 ∈ ℤ )
10 8 9 syl ( 𝜑𝑁 ∈ ℤ )
11 uzid ( 𝑁 ∈ ℤ → 𝑁 ∈ ( ℤ𝑁 ) )
12 11 2 eleqtrrdi ( 𝑁 ∈ ℤ → 𝑁𝑊 )
13 10 12 syl ( 𝜑𝑁𝑊 )
14 simpr ( ( 𝜑𝑘 = 𝑁 ) → 𝑘 = 𝑁 )
15 14 eleq1d ( ( 𝜑𝑘 = 𝑁 ) → ( 𝑘𝑊𝑁𝑊 ) )
16 14 fveq2d ( ( 𝜑𝑘 = 𝑁 ) → ( 𝐹𝑘 ) = ( 𝐹𝑁 ) )
17 16 fveq2d ( ( 𝜑𝑘 = 𝑁 ) → ( abs ‘ ( 𝐹𝑘 ) ) = ( abs ‘ ( 𝐹𝑁 ) ) )
18 17 breq2d ( ( 𝜑𝑘 = 𝑁 ) → ( 0 < ( abs ‘ ( 𝐹𝑘 ) ) ↔ 0 < ( abs ‘ ( 𝐹𝑁 ) ) ) )
19 15 18 imbi12d ( ( 𝜑𝑘 = 𝑁 ) → ( ( 𝑘𝑊 → 0 < ( abs ‘ ( 𝐹𝑘 ) ) ) ↔ ( 𝑁𝑊 → 0 < ( abs ‘ ( 𝐹𝑁 ) ) ) ) )
20 2 eleq2i ( 𝑘𝑊𝑘 ∈ ( ℤ𝑁 ) )
21 1 uztrn2 ( ( 𝑁𝑍𝑘 ∈ ( ℤ𝑁 ) ) → 𝑘𝑍 )
22 20 21 sylan2b ( ( 𝑁𝑍𝑘𝑊 ) → 𝑘𝑍 )
23 3 22 sylan ( ( 𝜑𝑘𝑊 ) → 𝑘𝑍 )
24 23 5 syldan ( ( 𝜑𝑘𝑊 ) → ( 𝐹𝑘 ) ∈ ℂ )
25 absgt0 ( ( 𝐹𝑘 ) ∈ ℂ → ( ( 𝐹𝑘 ) ≠ 0 ↔ 0 < ( abs ‘ ( 𝐹𝑘 ) ) ) )
26 24 25 syl ( ( 𝜑𝑘𝑊 ) → ( ( 𝐹𝑘 ) ≠ 0 ↔ 0 < ( abs ‘ ( 𝐹𝑘 ) ) ) )
27 6 26 mpbid ( ( 𝜑𝑘𝑊 ) → 0 < ( abs ‘ ( 𝐹𝑘 ) ) )
28 27 ex ( 𝜑 → ( 𝑘𝑊 → 0 < ( abs ‘ ( 𝐹𝑘 ) ) ) )
29 3 19 28 vtocld ( 𝜑 → ( 𝑁𝑊 → 0 < ( abs ‘ ( 𝐹𝑁 ) ) ) )
30 13 29 mpd ( 𝜑 → 0 < ( abs ‘ ( 𝐹𝑁 ) ) )
31 0red ( 𝜑 → 0 ∈ ℝ )
32 14 eleq1d ( ( 𝜑𝑘 = 𝑁 ) → ( 𝑘𝑍𝑁𝑍 ) )
33 16 eleq1d ( ( 𝜑𝑘 = 𝑁 ) → ( ( 𝐹𝑘 ) ∈ ℂ ↔ ( 𝐹𝑁 ) ∈ ℂ ) )
34 32 33 imbi12d ( ( 𝜑𝑘 = 𝑁 ) → ( ( 𝑘𝑍 → ( 𝐹𝑘 ) ∈ ℂ ) ↔ ( 𝑁𝑍 → ( 𝐹𝑁 ) ∈ ℂ ) ) )
35 5 ex ( 𝜑 → ( 𝑘𝑍 → ( 𝐹𝑘 ) ∈ ℂ ) )
36 3 34 35 vtocld ( 𝜑 → ( 𝑁𝑍 → ( 𝐹𝑁 ) ∈ ℂ ) )
37 3 36 mpd ( 𝜑 → ( 𝐹𝑁 ) ∈ ℂ )
38 37 abscld ( 𝜑 → ( abs ‘ ( 𝐹𝑁 ) ) ∈ ℝ )
39 31 38 ltnled ( 𝜑 → ( 0 < ( abs ‘ ( 𝐹𝑁 ) ) ↔ ¬ ( abs ‘ ( 𝐹𝑁 ) ) ≤ 0 ) )
40 30 39 mpbid ( 𝜑 → ¬ ( abs ‘ ( 𝐹𝑁 ) ) ≤ 0 )
41 10 adantr ( ( 𝜑𝐹 ⇝ 0 ) → 𝑁 ∈ ℤ )
42 38 adantr ( ( 𝜑𝐹 ⇝ 0 ) → ( abs ‘ ( 𝐹𝑁 ) ) ∈ ℝ )
43 simpr ( ( 𝜑𝐹 ⇝ 0 ) → 𝐹 ⇝ 0 )
44 2 fvexi 𝑊 ∈ V
45 44 mptex ( 𝑖𝑊 ↦ ( abs ‘ ( 𝐹𝑖 ) ) ) ∈ V
46 45 a1i ( ( 𝜑𝐹 ⇝ 0 ) → ( 𝑖𝑊 ↦ ( abs ‘ ( 𝐹𝑖 ) ) ) ∈ V )
47 24 adantlr ( ( ( 𝜑𝐹 ⇝ 0 ) ∧ 𝑘𝑊 ) → ( 𝐹𝑘 ) ∈ ℂ )
48 eqidd ( ( ( 𝜑𝐹 ⇝ 0 ) ∧ 𝑘𝑊 ) → ( 𝑖𝑊 ↦ ( abs ‘ ( 𝐹𝑖 ) ) ) = ( 𝑖𝑊 ↦ ( abs ‘ ( 𝐹𝑖 ) ) ) )
49 simpr ( ( ( ( 𝜑𝐹 ⇝ 0 ) ∧ 𝑘𝑊 ) ∧ 𝑖 = 𝑘 ) → 𝑖 = 𝑘 )
50 49 fveq2d ( ( ( ( 𝜑𝐹 ⇝ 0 ) ∧ 𝑘𝑊 ) ∧ 𝑖 = 𝑘 ) → ( 𝐹𝑖 ) = ( 𝐹𝑘 ) )
51 50 fveq2d ( ( ( ( 𝜑𝐹 ⇝ 0 ) ∧ 𝑘𝑊 ) ∧ 𝑖 = 𝑘 ) → ( abs ‘ ( 𝐹𝑖 ) ) = ( abs ‘ ( 𝐹𝑘 ) ) )
52 simpr ( ( ( 𝜑𝐹 ⇝ 0 ) ∧ 𝑘𝑊 ) → 𝑘𝑊 )
53 fvex ( abs ‘ ( 𝐹𝑘 ) ) ∈ V
54 53 a1i ( ( ( 𝜑𝐹 ⇝ 0 ) ∧ 𝑘𝑊 ) → ( abs ‘ ( 𝐹𝑘 ) ) ∈ V )
55 48 51 52 54 fvmptd ( ( ( 𝜑𝐹 ⇝ 0 ) ∧ 𝑘𝑊 ) → ( ( 𝑖𝑊 ↦ ( abs ‘ ( 𝐹𝑖 ) ) ) ‘ 𝑘 ) = ( abs ‘ ( 𝐹𝑘 ) ) )
56 2 43 46 41 47 55 climabs ( ( 𝜑𝐹 ⇝ 0 ) → ( 𝑖𝑊 ↦ ( abs ‘ ( 𝐹𝑖 ) ) ) ⇝ ( abs ‘ 0 ) )
57 abs0 ( abs ‘ 0 ) = 0
58 56 57 breqtrdi ( ( 𝜑𝐹 ⇝ 0 ) → ( 𝑖𝑊 ↦ ( abs ‘ ( 𝐹𝑖 ) ) ) ⇝ 0 )
59 47 abscld ( ( ( 𝜑𝐹 ⇝ 0 ) ∧ 𝑘𝑊 ) → ( abs ‘ ( 𝐹𝑘 ) ) ∈ ℝ )
60 55 59 eqeltrd ( ( ( 𝜑𝐹 ⇝ 0 ) ∧ 𝑘𝑊 ) → ( ( 𝑖𝑊 ↦ ( abs ‘ ( 𝐹𝑖 ) ) ) ‘ 𝑘 ) ∈ ℝ )
61 2fveq3 ( 𝑖 = 𝑁 → ( abs ‘ ( 𝐹𝑖 ) ) = ( abs ‘ ( 𝐹𝑁 ) ) )
62 61 breq2d ( 𝑖 = 𝑁 → ( ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑖 ) ) ↔ ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑁 ) ) ) )
63 62 imbi2d ( 𝑖 = 𝑁 → ( ( 𝜑 → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑖 ) ) ) ↔ ( 𝜑 → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑁 ) ) ) ) )
64 2fveq3 ( 𝑖 = 𝑘 → ( abs ‘ ( 𝐹𝑖 ) ) = ( abs ‘ ( 𝐹𝑘 ) ) )
65 64 breq2d ( 𝑖 = 𝑘 → ( ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑖 ) ) ↔ ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) ) )
66 65 imbi2d ( 𝑖 = 𝑘 → ( ( 𝜑 → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑖 ) ) ) ↔ ( 𝜑 → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) ) ) )
67 2fveq3 ( 𝑖 = ( 𝑘 + 1 ) → ( abs ‘ ( 𝐹𝑖 ) ) = ( abs ‘ ( 𝐹 ‘ ( 𝑘 + 1 ) ) ) )
68 67 breq2d ( 𝑖 = ( 𝑘 + 1 ) → ( ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑖 ) ) ↔ ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹 ‘ ( 𝑘 + 1 ) ) ) ) )
69 68 imbi2d ( 𝑖 = ( 𝑘 + 1 ) → ( ( 𝜑 → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑖 ) ) ) ↔ ( 𝜑 → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹 ‘ ( 𝑘 + 1 ) ) ) ) ) )
70 38 adantr ( ( 𝜑𝑁 ∈ ℤ ) → ( abs ‘ ( 𝐹𝑁 ) ) ∈ ℝ )
71 70 leidd ( ( 𝜑𝑁 ∈ ℤ ) → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑁 ) ) )
72 71 expcom ( 𝑁 ∈ ℤ → ( 𝜑 → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑁 ) ) ) )
73 38 ad2antrr ( ( ( 𝜑𝑘𝑊 ) ∧ ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) ) → ( abs ‘ ( 𝐹𝑁 ) ) ∈ ℝ )
74 24 adantr ( ( ( 𝜑𝑘𝑊 ) ∧ ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) ) → ( 𝐹𝑘 ) ∈ ℂ )
75 74 abscld ( ( ( 𝜑𝑘𝑊 ) ∧ ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) ) → ( abs ‘ ( 𝐹𝑘 ) ) ∈ ℝ )
76 2 peano2uzs ( 𝑘𝑊 → ( 𝑘 + 1 ) ∈ 𝑊 )
77 ovex ( 𝑘 + 1 ) ∈ V
78 eleq1 ( 𝑖 = ( 𝑘 + 1 ) → ( 𝑖𝑊 ↔ ( 𝑘 + 1 ) ∈ 𝑊 ) )
79 78 anbi2d ( 𝑖 = ( 𝑘 + 1 ) → ( ( 𝜑𝑖𝑊 ) ↔ ( 𝜑 ∧ ( 𝑘 + 1 ) ∈ 𝑊 ) ) )
80 fveq2 ( 𝑖 = ( 𝑘 + 1 ) → ( 𝐹𝑖 ) = ( 𝐹 ‘ ( 𝑘 + 1 ) ) )
81 80 eleq1d ( 𝑖 = ( 𝑘 + 1 ) → ( ( 𝐹𝑖 ) ∈ ℂ ↔ ( 𝐹 ‘ ( 𝑘 + 1 ) ) ∈ ℂ ) )
82 79 81 imbi12d ( 𝑖 = ( 𝑘 + 1 ) → ( ( ( 𝜑𝑖𝑊 ) → ( 𝐹𝑖 ) ∈ ℂ ) ↔ ( ( 𝜑 ∧ ( 𝑘 + 1 ) ∈ 𝑊 ) → ( 𝐹 ‘ ( 𝑘 + 1 ) ) ∈ ℂ ) ) )
83 eleq1 ( 𝑘 = 𝑖 → ( 𝑘𝑊𝑖𝑊 ) )
84 83 anbi2d ( 𝑘 = 𝑖 → ( ( 𝜑𝑘𝑊 ) ↔ ( 𝜑𝑖𝑊 ) ) )
85 fveq2 ( 𝑘 = 𝑖 → ( 𝐹𝑘 ) = ( 𝐹𝑖 ) )
86 85 eleq1d ( 𝑘 = 𝑖 → ( ( 𝐹𝑘 ) ∈ ℂ ↔ ( 𝐹𝑖 ) ∈ ℂ ) )
87 84 86 imbi12d ( 𝑘 = 𝑖 → ( ( ( 𝜑𝑘𝑊 ) → ( 𝐹𝑘 ) ∈ ℂ ) ↔ ( ( 𝜑𝑖𝑊 ) → ( 𝐹𝑖 ) ∈ ℂ ) ) )
88 87 24 chvarvv ( ( 𝜑𝑖𝑊 ) → ( 𝐹𝑖 ) ∈ ℂ )
89 77 82 88 vtocl ( ( 𝜑 ∧ ( 𝑘 + 1 ) ∈ 𝑊 ) → ( 𝐹 ‘ ( 𝑘 + 1 ) ) ∈ ℂ )
90 76 89 sylan2 ( ( 𝜑𝑘𝑊 ) → ( 𝐹 ‘ ( 𝑘 + 1 ) ) ∈ ℂ )
91 90 adantr ( ( ( 𝜑𝑘𝑊 ) ∧ ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) ) → ( 𝐹 ‘ ( 𝑘 + 1 ) ) ∈ ℂ )
92 91 abscld ( ( ( 𝜑𝑘𝑊 ) ∧ ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) ) → ( abs ‘ ( 𝐹 ‘ ( 𝑘 + 1 ) ) ) ∈ ℝ )
93 simpr ( ( ( 𝜑𝑘𝑊 ) ∧ ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) ) → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) )
94 7 adantr ( ( ( 𝜑𝑘𝑊 ) ∧ ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) ) → ( abs ‘ ( 𝐹𝑘 ) ) ≤ ( abs ‘ ( 𝐹 ‘ ( 𝑘 + 1 ) ) ) )
95 73 75 92 93 94 letrd ( ( ( 𝜑𝑘𝑊 ) ∧ ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) ) → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹 ‘ ( 𝑘 + 1 ) ) ) )
96 95 ex ( ( 𝜑𝑘𝑊 ) → ( ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹 ‘ ( 𝑘 + 1 ) ) ) ) )
97 20 96 sylan2br ( ( 𝜑𝑘 ∈ ( ℤ𝑁 ) ) → ( ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹 ‘ ( 𝑘 + 1 ) ) ) ) )
98 97 expcom ( 𝑘 ∈ ( ℤ𝑁 ) → ( 𝜑 → ( ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹 ‘ ( 𝑘 + 1 ) ) ) ) ) )
99 98 a2d ( 𝑘 ∈ ( ℤ𝑁 ) → ( ( 𝜑 → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) ) → ( 𝜑 → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹 ‘ ( 𝑘 + 1 ) ) ) ) ) )
100 63 66 69 66 72 99 uzind4 ( 𝑘 ∈ ( ℤ𝑁 ) → ( 𝜑 → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) ) )
101 100 impcom ( ( 𝜑𝑘 ∈ ( ℤ𝑁 ) ) → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) )
102 20 101 sylan2b ( ( 𝜑𝑘𝑊 ) → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) )
103 102 adantlr ( ( ( 𝜑𝐹 ⇝ 0 ) ∧ 𝑘𝑊 ) → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( abs ‘ ( 𝐹𝑘 ) ) )
104 103 55 breqtrrd ( ( ( 𝜑𝐹 ⇝ 0 ) ∧ 𝑘𝑊 ) → ( abs ‘ ( 𝐹𝑁 ) ) ≤ ( ( 𝑖𝑊 ↦ ( abs ‘ ( 𝐹𝑖 ) ) ) ‘ 𝑘 ) )
105 2 41 42 58 60 104 climlec2 ( ( 𝜑𝐹 ⇝ 0 ) → ( abs ‘ ( 𝐹𝑁 ) ) ≤ 0 )
106 40 105 mtand ( 𝜑 → ¬ 𝐹 ⇝ 0 )
107 eluzel2 ( 𝑁 ∈ ( ℤ𝑀 ) → 𝑀 ∈ ℤ )
108 8 107 syl ( 𝜑𝑀 ∈ ℤ )
109 108 adantr ( ( 𝜑 ∧ seq 𝑀 ( + , 𝐹 ) ∈ dom ⇝ ) → 𝑀 ∈ ℤ )
110 4 adantr ( ( 𝜑 ∧ seq 𝑀 ( + , 𝐹 ) ∈ dom ⇝ ) → 𝐹𝑉 )
111 simpr ( ( 𝜑 ∧ seq 𝑀 ( + , 𝐹 ) ∈ dom ⇝ ) → seq 𝑀 ( + , 𝐹 ) ∈ dom ⇝ )
112 5 adantlr ( ( ( 𝜑 ∧ seq 𝑀 ( + , 𝐹 ) ∈ dom ⇝ ) ∧ 𝑘𝑍 ) → ( 𝐹𝑘 ) ∈ ℂ )
113 1 109 110 111 112 serf0 ( ( 𝜑 ∧ seq 𝑀 ( + , 𝐹 ) ∈ dom ⇝ ) → 𝐹 ⇝ 0 )
114 106 113 mtand ( 𝜑 → ¬ seq 𝑀 ( + , 𝐹 ) ∈ dom ⇝ )
115 df-nel ( seq 𝑀 ( + , 𝐹 ) ∉ dom ⇝ ↔ ¬ seq 𝑀 ( + , 𝐹 ) ∈ dom ⇝ )
116 114 115 sylibr ( 𝜑 → seq 𝑀 ( + , 𝐹 ) ∉ dom ⇝ )