Metamath Proof Explorer


Theorem radcnvrat

Description: Let L be the limit, if one exists, of the ratio ( abs( ( A( k + 1 ) ) / ( Ak ) ) ) (as in the ratio test cvgdvgrat ) as k increases. Then the radius of convergence of power series sum_ n e. NN0 ( ( An ) x. ( x ^ n ) ) is ( 1 / L ) if L is nonzero. Proof "The limit involved in the ratio test..." in https://en.wikipedia.org/wiki/Radius_of_convergence —a few lines that evidently hide quite an involved process to confirm. (Contributed by Steve Rodriguez, 8-Mar-2020)

Ref Expression
Hypotheses radcnvrat.g G=xn0Anxn
radcnvrat.a φA:0
radcnvrat.r R=supr|seq0+Grdom*<
radcnvrat.rat D=k0Ak+1Ak
radcnvrat.z Z=M
radcnvrat.m φM0
radcnvrat.n0 φkZAk0
radcnvrat.l φDL
radcnvrat.ln0 φL0
Assertion radcnvrat φR=1L

Proof

Step Hyp Ref Expression
1 radcnvrat.g G=xn0Anxn
2 radcnvrat.a φA:0
3 radcnvrat.r R=supr|seq0+Grdom*<
4 radcnvrat.rat D=k0Ak+1Ak
5 radcnvrat.z Z=M
6 radcnvrat.m φM0
7 radcnvrat.n0 φkZAk0
8 radcnvrat.l φDL
9 radcnvrat.ln0 φL0
10 xrltso <Or*
11 10 a1i φ<Or*
12 6 nn0zd φM
13 5 reseq2i DZ=DM
14 nn0ex 0V
15 14 mptex k0Ak+1AkV
16 4 15 eqeltri DV
17 climres MDVDMLDL
18 12 16 17 sylancl φDMLDL
19 8 18 mpbird φDML
20 13 19 eqbrtrid φDZL
21 4 reseq1i DZ=k0Ak+1AkZ
22 eluznn0 M0kMk0
23 6 22 sylan φkMk0
24 23 ex φkMk0
25 24 ssrdv φM0
26 5 25 eqsstrid φZ0
27 26 resmptd φk0Ak+1AkZ=kZAk+1Ak
28 21 27 eqtrid φDZ=kZAk+1Ak
29 fvexd φkZAk+1AkV
30 28 29 fvmpt2d φkZDZk=Ak+1Ak
31 5 peano2uzs kZk+1Z
32 26 sselda φk+1Zk+10
33 2 ffvelcdmda φk+10Ak+1
34 32 33 syldan φk+1ZAk+1
35 31 34 sylan2 φkZAk+1
36 26 sselda φkZk0
37 2 ffvelcdmda φk0Ak
38 36 37 syldan φkZAk
39 35 38 7 divcld φkZAk+1Ak
40 39 abscld φkZAk+1Ak
41 30 40 eqeltrd φkZDZk
42 5 12 20 41 climrecl φL
43 42 9 rereccld φ1L
44 43 rexrd φ1L*
45 simpr φxr|seq0+Grdomxr|seq0+Grdom
46 elrabi xr|seq0+Grdomx
47 43 adantr φx1L
48 recn xx
49 48 abscld xx
50 49 adantl φxx
51 47 50 ltlend φx1L<x1Lxx1L
52 51 simplbda φx1L<xx1L
53 51 adantr φxx1L1L<x1Lxx1L
54 simpr φxx1Lx1L
55 54 biantrud φxx1L1Lx1Lxx1L
56 47 50 lenltd φx1Lx¬x<1L
57 56 adantr φxx1L1Lx¬x<1L
58 53 55 57 3bitr2d φxx1L1L<x¬x<1L
59 1cnd φx1
60 50 recnd φxx
61 42 recnd φL
62 61 adantr φxL
63 9 adantr φxL0
64 59 60 62 63 divmul3d φx1L=x1=xL
65 eqcom 1L=xx=1L
66 eqcom 1=xLxL=1
67 64 65 66 3bitr3g φxx=1LxL=1
68 67 necon3bid φxx1LxL1
69 68 biimpa φxx1LxL1
70 1red φx1
71 fvres kZDZk=Dk
72 71 adantl φkZDZk=Dk
73 72 41 eqeltrrd φkZDk
74 39 absge0d φkZ0Ak+1Ak
75 74 30 breqtrrd φkZ0DZk
76 75 72 breqtrd φkZ0Dk
77 5 12 8 73 76 climge0 φ0L
78 42 77 9 ne0gt0d φ0<L
79 42 78 elrpd φL+
80 79 adantr φxL+
81 50 70 80 ltmuldivd φxxL<1x<1L
82 81 adantr φxxL1xL<1x<1L
83 elun x00x0x0
84 inundif 00=
85 84 eleq2i x00x
86 83 85 bitr3i x0x0x
87 elin x0xx0
88 87 simprbi x0x0
89 elsni x0x=0
90 88 89 syl x0x=0
91 fveq2 x=0x=0
92 abs0 0=0
93 91 92 eqtrdi x=0x=0
94 93 oveq1d x=0xL=0L
95 61 mul02d φ0L=0
96 94 95 sylan9eqr φx=0xL=0
97 0lt1 0<1
98 96 97 eqbrtrdi φx=0xL<1
99 1 2 radcnv0 φ0r|seq0+Grdom
100 eleq1 x=0xr|seq0+Grdom0r|seq0+Grdom
101 99 100 syl5ibrcom φx=0xr|seq0+Grdom
102 101 imp φx=0xr|seq0+Grdom
103 98 102 2thd φx=0xL<1xr|seq0+Grdom
104 90 103 sylan2 φx0xL<1xr|seq0+Grdom
105 104 adantlr φxL1x0xL<1xr|seq0+Grdom
106 ax-resscn
107 ssdif 00
108 106 107 ax-mp 00
109 108 sseli x0x0
110 nn0uz 0=0
111 6 ad2antrr φx0xL1M0
112 fvexd φx0xL1GxV
113 eldifi x0x
114 1 a1i φG=xn0Anxn
115 14 mptex n0AnxnV
116 115 a1i φxn0AnxnV
117 114 116 fvmpt2d φxGx=n0Anxn
118 117 adantr φxk0Gx=n0Anxn
119 fveq2 n=kAn=Ak
120 oveq2 n=kxn=xk
121 119 120 oveq12d n=kAnxn=Akxk
122 121 adantl φxk0n=kAnxn=Akxk
123 simpr φxk0k0
124 ovexd φxk0AkxkV
125 118 122 123 124 fvmptd φxk0Gxk=Akxk
126 37 adantlr φxk0Ak
127 simplr φxk0x
128 127 123 expcld φxk0xk
129 126 128 mulcld φxk0Akxk
130 125 129 eqeltrd φxk0Gxk
131 113 130 sylanl2 φx0k0Gxk
132 131 adantlr φx0xL1k0Gxk
133 36 adantlr φxkZk0
134 133 125 syldan φxkZGxk=Akxk
135 113 134 sylanl2 φx0kZGxk=Akxk
136 38 adantlr φx0kZAk
137 113 adantl φx0x
138 137 adantr φx0kZx
139 36 adantlr φx0kZk0
140 138 139 expcld φx0kZxk
141 7 adantlr φx0kZAk0
142 eldifsni x0x0
143 142 ad2antlr φx0kZx0
144 139 nn0zd φx0kZk
145 138 143 144 expne0d φx0kZxk0
146 136 140 141 145 mulne0d φx0kZAkxk0
147 135 146 eqnetrd φx0kZGxk0
148 147 adantlr φx0xL1kZGxk0
149 fvoveq1 n=kGxn+1=Gxk+1
150 fveq2 n=kGxn=Gxk
151 149 150 oveq12d n=kGxn+1Gxn=Gxk+1Gxk
152 151 fveq2d n=kGxn+1Gxn=Gxk+1Gxk
153 152 cbvmptv nZGxn+1Gxn=kZGxk+1Gxk
154 5 reseq2i n0Gxn+1GxnZ=n0Gxn+1GxnM
155 26 adantr φx0Z0
156 155 resmptd φx0n0Gxn+1GxnZ=nZGxn+1Gxn
157 154 156 eqtr3id φx0n0Gxn+1GxnM=nZGxn+1Gxn
158 12 adantr φx0M
159 8 adantr φx0DL
160 137 abscld φx0x
161 160 recnd φx0x
162 14 mptex n0Gxn+1GxnV
163 162 a1i φx0n0Gxn+1GxnV
164 73 recnd φkZDk
165 164 adantlr φx0kZDk
166 eqidd φx0kZn0Gxn+1Gxn=n0Gxn+1Gxn
167 152 adantl φx0kZn=kGxn+1Gxn=Gxk+1Gxk
168 fvexd φx0kZGxk+1GxkV
169 166 167 139 168 fvmptd φx0kZn0Gxn+1Gxnk=Gxk+1Gxk
170 117 adantr φxkZGx=n0Anxn
171 simpr φxkZn=k+1n=k+1
172 171 fveq2d φxkZn=k+1An=Ak+1
173 171 oveq2d φxkZn=k+1xn=xk+1
174 172 173 oveq12d φxkZn=k+1Anxn=Ak+1xk+1
175 1nn0 10
176 175 a1i φxkZ10
177 133 176 nn0addcld φxkZk+10
178 ovexd φxkZAk+1xk+1V
179 170 174 177 178 fvmptd φxkZGxk+1=Ak+1xk+1
180 121 adantl φxkZn=kAnxn=Akxk
181 ovexd φxkZAkxkV
182 170 180 133 181 fvmptd φxkZGxk=Akxk
183 179 182 oveq12d φxkZGxk+1Gxk=Ak+1xk+1Akxk
184 113 183 sylanl2 φx0kZGxk+1Gxk=Ak+1xk+1Akxk
185 35 adantlr φx0kZAk+1
186 113 177 sylanl2 φx0kZk+10
187 138 186 expcld φx0kZxk+1
188 185 136 187 140 141 145 divmuldivd φx0kZAk+1Akxk+1xk=Ak+1xk+1Akxk
189 139 nn0cnd φx0kZk
190 1cnd φx0kZ1
191 189 190 pncan2d φx0kZk+1-k=1
192 191 oveq2d φx0kZxk+1-k=x1
193 186 nn0zd φx0kZk+1
194 138 143 144 193 expsubd φx0kZxk+1-k=xk+1xk
195 138 exp1d φx0kZx1=x
196 192 194 195 3eqtr3d φx0kZxk+1xk=x
197 196 oveq2d φx0kZAk+1Akxk+1xk=Ak+1Akx
198 184 188 197 3eqtr2d φx0kZGxk+1Gxk=Ak+1Akx
199 198 fveq2d φx0kZGxk+1Gxk=Ak+1Akx
200 39 adantlr φx0kZAk+1Ak
201 200 138 absmuld φx0kZAk+1Akx=Ak+1Akx
202 169 199 201 3eqtrd φx0kZn0Gxn+1Gxnk=Ak+1Akx
203 72 30 eqtr3d φkZDk=Ak+1Ak
204 203 adantlr φx0kZDk=Ak+1Ak
205 204 eqcomd φx0kZAk+1Ak=Dk
206 205 oveq1d φx0kZAk+1Akx=Dkx
207 161 adantr φx0kZx
208 165 207 mulcomd φx0kZDkx=xDk
209 202 206 208 3eqtrd φx0kZn0Gxn+1Gxnk=xDk
210 5 158 159 161 163 165 209 climmulc2 φx0n0Gxn+1GxnxL
211 climres Mn0Gxn+1GxnVn0Gxn+1GxnMxLn0Gxn+1GxnxL
212 158 162 211 sylancl φx0n0Gxn+1GxnMxLn0Gxn+1GxnxL
213 210 212 mpbird φx0n0Gxn+1GxnMxL
214 157 213 eqbrtrrd φx0nZGxn+1GxnxL
215 214 adantr φx0xL1nZGxn+1GxnxL
216 simpr φx0xL1xL1
217 110 5 111 112 132 148 153 215 216 cvgdvgrat φx0xL1xL<1seq0+Gxdom
218 109 217 sylanl2 φx0xL1xL<1seq0+Gxdom
219 eldifi x0x
220 fveq2 r=xGr=Gx
221 220 seqeq3d r=xseq0+Gr=seq0+Gx
222 221 eleq1d r=xseq0+Grdomseq0+Gxdom
223 222 elrab3 xxr|seq0+Grdomseq0+Gxdom
224 219 223 syl x0xr|seq0+Grdomseq0+Gxdom
225 224 ad2antlr φx0xL1xr|seq0+Grdomseq0+Gxdom
226 218 225 bitr4d φx0xL1xL<1xr|seq0+Grdom
227 226 an32s φxL1x0xL<1xr|seq0+Grdom
228 105 227 jaodan φxL1x0x0xL<1xr|seq0+Grdom
229 86 228 sylan2br φxL1xxL<1xr|seq0+Grdom
230 229 an32s φxxL1xL<1xr|seq0+Grdom
231 82 230 bitr3d φxxL1x<1Lxr|seq0+Grdom
232 69 231 syldan φxx1Lx<1Lxr|seq0+Grdom
233 232 notbid φxx1L¬x<1L¬xr|seq0+Grdom
234 58 233 bitrd φxx1L1L<x¬xr|seq0+Grdom
235 234 biimpd φxx1L1L<x¬xr|seq0+Grdom
236 235 impancom φx1L<xx1L¬xr|seq0+Grdom
237 52 236 mpd φx1L<x¬xr|seq0+Grdom
238 237 ex φx1L<x¬xr|seq0+Grdom
239 238 con2d φxxr|seq0+Grdom¬1L<x
240 47 adantr φx1L<x1L
241 simplr φx1L<xx
242 50 adantr φx1L<xx
243 simpr φx1L<x1L<x
244 241 leabsd φx1L<xxx
245 240 241 242 243 244 ltletrd φx1L<x1L<x
246 245 ex φx1L<x1L<x
247 239 246 nsyld φxxr|seq0+Grdom¬1L<x
248 46 247 sylan2 φxr|seq0+Grdomxr|seq0+Grdom¬1L<x
249 45 248 mpd φxr|seq0+Grdom¬1L<x
250 43 renegcld φ1L
251 250 rexrd φ1L*
252 iooss1 1L*1Lxx1L1L1L
253 251 252 sylan φ1Lxx1L1L1L
254 253 adantlr φx*x<1L1Lxx1L1L1L
255 eliooord kx1Lx<kk<1L
256 255 simpld kx1Lx<k
257 256 rgen kx1Lx<k
258 ioon0 x*1L*x1Lx<1L
259 44 258 sylan2 x*φx1Lx<1L
260 259 ancoms φx*x1Lx<1L
261 260 biimpar φx*x<1Lx1L
262 r19.2zb x1Lkx1Lx<kkx1Lx<k
263 261 262 sylib φx*x<1Lkx1Lx<kkx1Lx<k
264 257 263 mpi φx*x<1Lkx1Lx<k
265 264 anasss φx*x<1Lkx1Lx<k
266 265 adantr φx*x<1L1Lxkx1Lx<k
267 ssrexv x1L1L1Lkx1Lx<kk1L1Lx<k
268 254 266 267 sylc φx*x<1L1Lxk1L1Lx<k
269 simplr φx*¬1Lxx*
270 xrltnle x*1L*x<1L¬1Lx
271 xrltle x*1L*x<1Lx1L
272 270 271 sylbird x*1L*¬1Lxx1L
273 251 272 sylan2 x*φ¬1Lxx1L
274 273 ancoms φx*¬1Lxx1L
275 274 imp φx*¬1Lxx1L
276 iooss1 x*x1L1L1Lx1L
277 269 275 276 syl2anc φx*¬1Lx1L1Lx1L
278 277 sselda φx*¬1Lxk1L1Lkx1L
279 278 256 syl φx*¬1Lxk1L1Lx<k
280 279 ralrimiva φx*¬1Lxk1L1Lx<k
281 42 78 recgt0d φ0<1L
282 43 43 281 281 addgt0d φ0<1L+1L
283 43 recnd φ1L
284 283 283 subnegd φ1L1L=1L+1L
285 282 284 breqtrrd φ0<1L1L
286 250 43 posdifd φ1L<1L0<1L1L
287 285 286 mpbird φ1L<1L
288 ioon0 1L*1L*1L1L1L<1L
289 251 44 288 syl2anc φ1L1L1L<1L
290 287 289 mpbird φ1L1L
291 r19.2zb 1L1Lk1L1Lx<kk1L1Lx<k
292 290 291 sylib φk1L1Lx<kk1L1Lx<k
293 292 ad2antrr φx*¬1Lxk1L1Lx<kk1L1Lx<k
294 280 293 mpd φx*¬1Lxk1L1Lx<k
295 294 adantlrr φx*x<1L¬1Lxk1L1Lx<k
296 268 295 pm2.61dan φx*x<1Lk1L1Lx<k
297 elioo2 1L*1L*x1L1Lx1L<xx<1L
298 251 44 297 syl2anc φx1L1Lx1L<xx<1L
299 298 biimpa φx1L1Lx1L<xx<1L
300 simpr φxx
301 300 47 absltd φxx<1L1L<xx<1L
302 50 adantr φxx<1Lx
303 simpr φxx<1Lx<1L
304 302 303 ltned φxx<1Lx1L
305 232 biimpd φxx1Lx<1Lxr|seq0+Grdom
306 305 impancom φxx<1Lx1Lxr|seq0+Grdom
307 304 306 mpd φxx<1Lxr|seq0+Grdom
308 307 ex φxx<1Lxr|seq0+Grdom
309 301 308 sylbird φx1L<xx<1Lxr|seq0+Grdom
310 309 impr φx1L<xx<1Lxr|seq0+Grdom
311 310 expcom x1L<xx<1Lφxr|seq0+Grdom
312 311 3impb x1L<xx<1Lφxr|seq0+Grdom
313 312 impcom φx1L<xx<1Lxr|seq0+Grdom
314 299 313 syldan φx1L1Lxr|seq0+Grdom
315 314 ex φx1L1Lxr|seq0+Grdom
316 315 ssrdv φ1L1Lr|seq0+Grdom
317 ssrexv 1L1Lr|seq0+Grdomk1L1Lx<kkr|seq0+Grdomx<k
318 316 317 syl φk1L1Lx<kkr|seq0+Grdomx<k
319 318 adantr φx*x<1Lk1L1Lx<kkr|seq0+Grdomx<k
320 296 319 mpd φx*x<1Lkr|seq0+Grdomx<k
321 11 44 249 320 eqsupd φsupr|seq0+Grdom*<=1L
322 3 321 eqtrid φR=1L