Metamath Proof Explorer


Theorem cvgdvgrat

Description: Ratio test for convergence and divergence of a complex infinite series. If the ratio R of the absolute values of successive terms in an infinite sequence F converges to less than one, then the infinite sum of the terms of F converges to a complex number; and if R convergesgreater then the sum diverges. This combined form of cvgrat and dvgrat directly uses the limit of the ratio.

(It also demonstrates how to use climi2 and absltd to transform a limit to an inequality cf. https://math.stackexchange.com/q/2215191 , and how to use r19.29a in a similar fashion to Mario Carneiro's proof sketch with rexlimdva at https://groups.google.com/g/metamath/c/2RPikOiXLMo .) (Contributed by Steve Rodriguez, 28-Feb-2020)

Ref Expression
Hypotheses cvgdvgrat.z Z = M
cvgdvgrat.w W = N
cvgdvgrat.n φ N Z
cvgdvgrat.f φ F V
cvgdvgrat.c φ k Z F k
cvgdvgrat.n0 φ k W F k 0
cvgdvgrat.r R = k W F k + 1 F k
cvgdvgrat.cvg φ R L
cvgdvgrat.n1 φ L 1
Assertion cvgdvgrat φ L < 1 seq M + F dom

Proof

Step Hyp Ref Expression
1 cvgdvgrat.z Z = M
2 cvgdvgrat.w W = N
3 cvgdvgrat.n φ N Z
4 cvgdvgrat.f φ F V
5 cvgdvgrat.c φ k Z F k
6 cvgdvgrat.n0 φ k W F k 0
7 cvgdvgrat.r R = k W F k + 1 F k
8 cvgdvgrat.cvg φ R L
9 cvgdvgrat.n1 φ L 1
10 eqid n = n
11 elioore r L 1 r
12 11 ad3antlr φ r L 1 n W k n F k + 1 r F k r
13 3 1 eleqtrdi φ N M
14 eluzelz N M N
15 13 14 syl φ N
16 7 a1i φ R = k W F k + 1 F k
17 2 peano2uzs k W k + 1 W
18 ovex k + 1 V
19 eleq1 i = k + 1 i W k + 1 W
20 19 anbi2d i = k + 1 φ i W φ k + 1 W
21 fveq2 i = k + 1 F i = F k + 1
22 21 eleq1d i = k + 1 F i F k + 1
23 20 22 imbi12d i = k + 1 φ i W F i φ k + 1 W F k + 1
24 eleq1 k = i k W i W
25 24 anbi2d k = i φ k W φ i W
26 fveq2 k = i F k = F i
27 26 eleq1d k = i F k F i
28 25 27 imbi12d k = i φ k W F k φ i W F i
29 2 eleq2i k W k N
30 1 uztrn2 N Z k N k Z
31 3 30 sylan φ k N k Z
32 29 31 sylan2b φ k W k Z
33 32 5 syldan φ k W F k
34 28 33 chvarvv φ i W F i
35 18 23 34 vtocl φ k + 1 W F k + 1
36 17 35 sylan2 φ k W F k + 1
37 36 33 6 divcld φ k W F k + 1 F k
38 37 abscld φ k W F k + 1 F k
39 16 38 fvmpt2d φ k W R k = F k + 1 F k
40 39 38 eqeltrd φ k W R k
41 2 15 8 40 climrecl φ L
42 41 rexrd φ L *
43 1xr 1 *
44 elioo2 L * 1 * r L 1 r L < r r < 1
45 42 43 44 sylancl φ r L 1 r L < r r < 1
46 45 biimpa φ r L 1 r L < r r < 1
47 46 simp3d φ r L 1 r < 1
48 47 ad2antrr φ r L 1 n W k n F k + 1 r F k r < 1
49 simplr φ r L 1 n W k n F k + 1 r F k n W
50 34 ex φ i W F i
51 50 ad3antrrr φ r L 1 n W k n F k + 1 r F k i W F i
52 51 imp φ r L 1 n W k n F k + 1 r F k i W F i
53 fvoveq1 k = i F k + 1 = F i + 1
54 53 fveq2d k = i F k + 1 = F i + 1
55 26 fveq2d k = i F k = F i
56 55 oveq2d k = i r F k = r F i
57 54 56 breq12d k = i F k + 1 r F k F i + 1 r F i
58 57 rspccva k n F k + 1 r F k i n F i + 1 r F i
59 58 adantll φ r L 1 n W k n F k + 1 r F k i n F i + 1 r F i
60 2 10 12 48 49 52 59 cvgrat φ r L 1 n W k n F k + 1 r F k seq N + F dom
61 15 adantr φ r L 1 N
62 46 simp2d φ r L 1 L < r
63 difrp L r L < r r L +
64 41 11 63 syl2an φ r L 1 L < r r L +
65 62 64 mpbid φ r L 1 r L +
66 39 adantlr φ r L 1 k W R k = F k + 1 F k
67 8 adantr φ r L 1 R L
68 2 61 65 66 67 climi2 φ r L 1 n W k n F k + 1 F k L < r L
69 2 uztrn2 n W k n k W
70 69 36 sylan2 φ n W k n F k + 1
71 70 anassrs φ n W k n F k + 1
72 71 adantllr φ r L 1 n W k n F k + 1
73 72 adantr φ r L 1 n W k n F k + 1 F k L < r L F k + 1
74 73 abscld φ r L 1 n W k n F k + 1 F k L < r L F k + 1
75 11 ad4antlr φ r L 1 n W k n F k + 1 F k L < r L r
76 69 33 sylan2 φ n W k n F k
77 76 anassrs φ n W k n F k
78 77 adantllr φ r L 1 n W k n F k
79 78 adantr φ r L 1 n W k n F k + 1 F k L < r L F k
80 79 abscld φ r L 1 n W k n F k + 1 F k L < r L F k
81 75 80 remulcld φ r L 1 n W k n F k + 1 F k L < r L r F k
82 69 6 sylan2 φ n W k n F k 0
83 82 anassrs φ n W k n F k 0
84 83 adantllr φ r L 1 n W k n F k 0
85 84 adantr φ r L 1 n W k n F k + 1 F k L < r L F k 0
86 73 79 85 absdivd φ r L 1 n W k n F k + 1 F k L < r L F k + 1 F k = F k + 1 F k
87 72 78 84 divcld φ r L 1 n W k n F k + 1 F k
88 87 abscld φ r L 1 n W k n F k + 1 F k
89 41 ad3antrrr φ r L 1 n W k n L
90 88 89 resubcld φ r L 1 n W k n F k + 1 F k L
91 11 ad3antlr φ r L 1 n W k n r
92 91 89 resubcld φ r L 1 n W k n r L
93 90 92 absltd φ r L 1 n W k n F k + 1 F k L < r L r L < F k + 1 F k L F k + 1 F k L < r L
94 93 simplbda φ r L 1 n W k n F k + 1 F k L < r L F k + 1 F k L < r L
95 73 79 85 divcld φ r L 1 n W k n F k + 1 F k L < r L F k + 1 F k
96 95 abscld φ r L 1 n W k n F k + 1 F k L < r L F k + 1 F k
97 41 ad4antr φ r L 1 n W k n F k + 1 F k L < r L L
98 96 75 97 ltsub1d φ r L 1 n W k n F k + 1 F k L < r L F k + 1 F k < r F k + 1 F k L < r L
99 94 98 mpbird φ r L 1 n W k n F k + 1 F k L < r L F k + 1 F k < r
100 86 99 eqbrtrrd φ r L 1 n W k n F k + 1 F k L < r L F k + 1 F k < r
101 79 85 absrpcld φ r L 1 n W k n F k + 1 F k L < r L F k +
102 74 75 101 ltdivmuld φ r L 1 n W k n F k + 1 F k L < r L F k + 1 F k < r F k + 1 < F k r
103 100 102 mpbid φ r L 1 n W k n F k + 1 F k L < r L F k + 1 < F k r
104 101 rpcnd φ r L 1 n W k n F k + 1 F k L < r L F k
105 75 recnd φ r L 1 n W k n F k + 1 F k L < r L r
106 104 105 mulcomd φ r L 1 n W k n F k + 1 F k L < r L F k r = r F k
107 103 106 breqtrd φ r L 1 n W k n F k + 1 F k L < r L F k + 1 < r F k
108 74 81 107 ltled φ r L 1 n W k n F k + 1 F k L < r L F k + 1 r F k
109 108 ex φ r L 1 n W k n F k + 1 F k L < r L F k + 1 r F k
110 109 ralimdva φ r L 1 n W k n F k + 1 F k L < r L k n F k + 1 r F k
111 110 reximdva φ r L 1 n W k n F k + 1 F k L < r L n W k n F k + 1 r F k
112 68 111 mpd φ r L 1 n W k n F k + 1 r F k
113 60 112 r19.29a φ r L 1 seq N + F dom
114 113 ralrimiva φ r L 1 seq N + F dom
115 114 adantr φ L < 1 r L 1 seq N + F dom
116 ioon0 L * 1 * L 1 L < 1
117 42 43 116 sylancl φ L 1 L < 1
118 117 biimpar φ L < 1 L 1
119 r19.3rzv L 1 seq N + F dom r L 1 seq N + F dom
120 118 119 syl φ L < 1 seq N + F dom r L 1 seq N + F dom
121 115 120 mpbird φ L < 1 seq N + F dom
122 1 3 5 iserex φ seq M + F dom seq N + F dom
123 122 adantr φ L < 1 seq M + F dom seq N + F dom
124 121 123 mpbird φ L < 1 seq M + F dom
125 124 ex φ L < 1 seq M + F dom
126 1red φ 1
127 41 126 lttri2d φ L 1 L < 1 1 < L
128 9 127 mpbid φ L < 1 1 < L
129 128 orcanai φ ¬ L < 1 1 < L
130 simplr φ 1 < L n W k n F k F k + 1 n W
131 4 ad3antrrr φ 1 < L n W k n F k F k + 1 F V
132 50 ad3antrrr φ 1 < L n W k n F k F k + 1 i W F i
133 132 imp φ 1 < L n W k n F k F k + 1 i W F i
134 2 uztrn2 n W i n i W
135 26 neeq1d k = i F k 0 F i 0
136 25 135 imbi12d k = i φ k W F k 0 φ i W F i 0
137 136 6 chvarvv φ i W F i 0
138 134 137 sylan2 φ n W i n F i 0
139 138 anassrs φ n W i n F i 0
140 139 adantllr φ 1 < L n W i n F i 0
141 140 adantlr φ 1 < L n W k n F k F k + 1 i n F i 0
142 55 54 breq12d k = i F k F k + 1 F i F i + 1
143 142 rspccva k n F k F k + 1 i n F i F i + 1
144 143 adantll φ 1 < L n W k n F k F k + 1 i n F i F i + 1
145 2 10 130 131 133 141 144 dvgrat φ 1 < L n W k n F k F k + 1 seq N + F dom
146 15 adantr φ 1 < L N
147 1re 1
148 difrp 1 L 1 < L L 1 +
149 147 41 148 sylancr φ 1 < L L 1 +
150 149 biimpa φ 1 < L L 1 +
151 39 adantlr φ 1 < L k W R k = F k + 1 F k
152 8 adantr φ 1 < L R L
153 2 146 150 151 152 climi2 φ 1 < L n W k n F k + 1 F k L < L 1
154 77 adantllr φ 1 < L n W k n F k
155 154 adantr φ 1 < L n W k n F k + 1 F k L < L 1 F k
156 155 abscld φ 1 < L n W k n F k + 1 F k L < L 1 F k
157 71 adantllr φ 1 < L n W k n F k + 1
158 157 adantr φ 1 < L n W k n F k + 1 F k L < L 1 F k + 1
159 158 abscld φ 1 < L n W k n F k + 1 F k L < L 1 F k + 1
160 83 adantllr φ 1 < L n W k n F k 0
161 160 adantr φ 1 < L n W k n F k + 1 F k L < L 1 F k 0
162 155 161 absrpcld φ 1 < L n W k n F k + 1 F k L < L 1 F k +
163 162 rpcnd φ 1 < L n W k n F k + 1 F k L < L 1 F k
164 163 mulid2d φ 1 < L n W k n F k + 1 F k L < L 1 1 F k = F k
165 41 ad4antr φ 1 < L n W k n F k + 1 F k L < L 1 L
166 165 recnd φ 1 < L n W k n F k + 1 F k L < L 1 L
167 1cnd φ 1 < L n W k n F k + 1 F k L < L 1 1
168 166 167 negsubdi2d φ 1 < L n W k n F k + 1 F k L < L 1 L 1 = 1 L
169 157 154 160 divcld φ 1 < L n W k n F k + 1 F k
170 169 abscld φ 1 < L n W k n F k + 1 F k
171 41 ad3antrrr φ 1 < L n W k n L
172 170 171 resubcld φ 1 < L n W k n F k + 1 F k L
173 1red φ 1 < L n W k n 1
174 171 173 resubcld φ 1 < L n W k n L 1
175 172 174 absltd φ 1 < L n W k n F k + 1 F k L < L 1 L 1 < F k + 1 F k L F k + 1 F k L < L 1
176 175 simprbda φ 1 < L n W k n F k + 1 F k L < L 1 L 1 < F k + 1 F k L
177 168 176 eqbrtrrd φ 1 < L n W k n F k + 1 F k L < L 1 1 L < F k + 1 F k L
178 1red φ 1 < L n W k n F k + 1 F k L < L 1 1
179 158 155 161 divcld φ 1 < L n W k n F k + 1 F k L < L 1 F k + 1 F k
180 179 abscld φ 1 < L n W k n F k + 1 F k L < L 1 F k + 1 F k
181 178 180 165 ltsub1d φ 1 < L n W k n F k + 1 F k L < L 1 1 < F k + 1 F k 1 L < F k + 1 F k L
182 177 181 mpbird φ 1 < L n W k n F k + 1 F k L < L 1 1 < F k + 1 F k
183 158 155 161 absdivd φ 1 < L n W k n F k + 1 F k L < L 1 F k + 1 F k = F k + 1 F k
184 182 183 breqtrd φ 1 < L n W k n F k + 1 F k L < L 1 1 < F k + 1 F k
185 178 159 162 ltmuldivd φ 1 < L n W k n F k + 1 F k L < L 1 1 F k < F k + 1 1 < F k + 1 F k
186 184 185 mpbird φ 1 < L n W k n F k + 1 F k L < L 1 1 F k < F k + 1
187 164 186 eqbrtrrd φ 1 < L n W k n F k + 1 F k L < L 1 F k < F k + 1
188 156 159 187 ltled φ 1 < L n W k n F k + 1 F k L < L 1 F k F k + 1
189 188 ex φ 1 < L n W k n F k + 1 F k L < L 1 F k F k + 1
190 189 ralimdva φ 1 < L n W k n F k + 1 F k L < L 1 k n F k F k + 1
191 190 reximdva φ 1 < L n W k n F k + 1 F k L < L 1 n W k n F k F k + 1
192 153 191 mpd φ 1 < L n W k n F k F k + 1
193 145 192 r19.29a φ 1 < L seq N + F dom
194 df-nel seq N + F dom ¬ seq N + F dom
195 193 194 sylib φ 1 < L ¬ seq N + F dom
196 122 adantr φ 1 < L seq M + F dom seq N + F dom
197 195 196 mtbird φ 1 < L ¬ seq M + F dom
198 129 197 syldan φ ¬ L < 1 ¬ seq M + F dom
199 198 ex φ ¬ L < 1 ¬ seq M + F dom
200 125 199 impcon4bid φ L < 1 seq M + F dom