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Description: The limit of a geometric series of reciprocals. (Contributed by Paul Chapman, 28-Dec-2007) (Revised by Mario Carneiro, 26-Apr-2014)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | georeclim.1 | |- ( ph -> A e. CC ) |
|
| georeclim.2 | |- ( ph -> 1 < ( abs ` A ) ) |
||
| georeclim.3 | |- ( ( ph /\ k e. NN0 ) -> ( F ` k ) = ( ( 1 / A ) ^ k ) ) |
||
| Assertion | georeclim | |- ( ph -> seq 0 ( + , F ) ~~> ( A / ( A - 1 ) ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | georeclim.1 | |- ( ph -> A e. CC ) |
|
| 2 | georeclim.2 | |- ( ph -> 1 < ( abs ` A ) ) |
|
| 3 | georeclim.3 | |- ( ( ph /\ k e. NN0 ) -> ( F ` k ) = ( ( 1 / A ) ^ k ) ) |
|
| 4 | 0le1 | |- 0 <_ 1 |
|
| 5 | 0re | |- 0 e. RR |
|
| 6 | 1re | |- 1 e. RR |
|
| 7 | 5 6 | lenlti | |- ( 0 <_ 1 <-> -. 1 < 0 ) |
| 8 | 4 7 | mpbi | |- -. 1 < 0 |
| 9 | fveq2 | |- ( A = 0 -> ( abs ` A ) = ( abs ` 0 ) ) |
|
| 10 | abs0 | |- ( abs ` 0 ) = 0 |
|
| 11 | 9 10 | eqtrdi | |- ( A = 0 -> ( abs ` A ) = 0 ) |
| 12 | 11 | breq2d | |- ( A = 0 -> ( 1 < ( abs ` A ) <-> 1 < 0 ) ) |
| 13 | 8 12 | mtbiri | |- ( A = 0 -> -. 1 < ( abs ` A ) ) |
| 14 | 13 | necon2ai | |- ( 1 < ( abs ` A ) -> A =/= 0 ) |
| 15 | 2 14 | syl | |- ( ph -> A =/= 0 ) |
| 16 | 1 15 | reccld | |- ( ph -> ( 1 / A ) e. CC ) |
| 17 | 1cnd | |- ( ph -> 1 e. CC ) |
|
| 18 | 17 1 15 | absdivd | |- ( ph -> ( abs ` ( 1 / A ) ) = ( ( abs ` 1 ) / ( abs ` A ) ) ) |
| 19 | abs1 | |- ( abs ` 1 ) = 1 |
|
| 20 | 19 | oveq1i | |- ( ( abs ` 1 ) / ( abs ` A ) ) = ( 1 / ( abs ` A ) ) |
| 21 | 18 20 | eqtrdi | |- ( ph -> ( abs ` ( 1 / A ) ) = ( 1 / ( abs ` A ) ) ) |
| 22 | 1 15 | absrpcld | |- ( ph -> ( abs ` A ) e. RR+ ) |
| 23 | 22 | recgt1d | |- ( ph -> ( 1 < ( abs ` A ) <-> ( 1 / ( abs ` A ) ) < 1 ) ) |
| 24 | 2 23 | mpbid | |- ( ph -> ( 1 / ( abs ` A ) ) < 1 ) |
| 25 | 21 24 | eqbrtrd | |- ( ph -> ( abs ` ( 1 / A ) ) < 1 ) |
| 26 | 16 25 3 | geolim | |- ( ph -> seq 0 ( + , F ) ~~> ( 1 / ( 1 - ( 1 / A ) ) ) ) |
| 27 | 1 17 1 15 | divsubdird | |- ( ph -> ( ( A - 1 ) / A ) = ( ( A / A ) - ( 1 / A ) ) ) |
| 28 | 1 15 | dividd | |- ( ph -> ( A / A ) = 1 ) |
| 29 | 28 | oveq1d | |- ( ph -> ( ( A / A ) - ( 1 / A ) ) = ( 1 - ( 1 / A ) ) ) |
| 30 | 27 29 | eqtrd | |- ( ph -> ( ( A - 1 ) / A ) = ( 1 - ( 1 / A ) ) ) |
| 31 | 30 | oveq2d | |- ( ph -> ( 1 / ( ( A - 1 ) / A ) ) = ( 1 / ( 1 - ( 1 / A ) ) ) ) |
| 32 | ax-1cn | |- 1 e. CC |
|
| 33 | subcl | |- ( ( A e. CC /\ 1 e. CC ) -> ( A - 1 ) e. CC ) |
|
| 34 | 1 32 33 | sylancl | |- ( ph -> ( A - 1 ) e. CC ) |
| 35 | 6 | ltnri | |- -. 1 < 1 |
| 36 | fveq2 | |- ( A = 1 -> ( abs ` A ) = ( abs ` 1 ) ) |
|
| 37 | 36 19 | eqtrdi | |- ( A = 1 -> ( abs ` A ) = 1 ) |
| 38 | 37 | breq2d | |- ( A = 1 -> ( 1 < ( abs ` A ) <-> 1 < 1 ) ) |
| 39 | 35 38 | mtbiri | |- ( A = 1 -> -. 1 < ( abs ` A ) ) |
| 40 | 39 | necon2ai | |- ( 1 < ( abs ` A ) -> A =/= 1 ) |
| 41 | 2 40 | syl | |- ( ph -> A =/= 1 ) |
| 42 | subeq0 | |- ( ( A e. CC /\ 1 e. CC ) -> ( ( A - 1 ) = 0 <-> A = 1 ) ) |
|
| 43 | 1 32 42 | sylancl | |- ( ph -> ( ( A - 1 ) = 0 <-> A = 1 ) ) |
| 44 | 43 | necon3bid | |- ( ph -> ( ( A - 1 ) =/= 0 <-> A =/= 1 ) ) |
| 45 | 41 44 | mpbird | |- ( ph -> ( A - 1 ) =/= 0 ) |
| 46 | 34 1 45 15 | recdivd | |- ( ph -> ( 1 / ( ( A - 1 ) / A ) ) = ( A / ( A - 1 ) ) ) |
| 47 | 31 46 | eqtr3d | |- ( ph -> ( 1 / ( 1 - ( 1 / A ) ) ) = ( A / ( A - 1 ) ) ) |
| 48 | 26 47 | breqtrd | |- ( ph -> seq 0 ( + , F ) ~~> ( A / ( A - 1 ) ) ) |