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Mathematics 10 Online
OpenStudy (anonymous):

Series question !

OpenStudy (anonymous):

Study the nature and find the sum of the following series: \[\sum_{n=2}^{\infty}\ln(1-\frac{ 1 }{ n^2 })\]

OpenStudy (anonymous):

\[S _{n}=\ln(\frac{ 3*8*15*...*n^2-1 }{ 4*9*16*...*n^2 })\]

OpenStudy (anonymous):

@ganeshie8 @Hero @Abhisar @.Sam. @Compassionate @nincompoop @eliassaab @ikram002p @Joel_the_boss @Coolsector @One098

ganeshie8 (ganeshie8):

http://www.ams.org/bookstore/pspdf/gsm-97-prev.pdf

ganeshie8 (ganeshie8):

\[\sum_{n=2}^{\infty}\ln\left(1-\frac{ 1 }{ n^2 }\right) = \ln \prod_{n=2}^{\infty}\left(1-\frac{ 1 }{ n^2 }\right) \]

OpenStudy (anonymous):

what's that pi sign never saw that It's the product ??????

ganeshie8 (ganeshie8):

its like sum sign

ganeshie8 (ganeshie8):

\[\prod_{n=1}^3 n = 1\times 2 \times 3\]

ganeshie8 (ganeshie8):

\[\prod_{n=1}^{10} n = 1\times 2 \times 3\times \cdots \times 10\]

OpenStudy (anonymous):

so it's the equivalent of the sum sign for products

ganeshie8 (ganeshie8):

Exactly!

OpenStudy (anonymous):

but how do you know that relationship ?

ganeshie8 (ganeshie8):

just expand it and see

OpenStudy (anonymous):

o I saw it actually look at my first posts

ganeshie8 (ganeshie8):

we use below log property : \[ \ln(a) + \ln(b) + \ln(c) + \cdots = \ln(a\times b\times c\times \cdots )\]

ganeshie8 (ganeshie8):

sum of logs = log of products

ganeshie8 (ganeshie8):

\[\sum_{n=2}^{\infty}\ln\left(1-\frac{ 1 }{ n^2 }\right) = \ln \prod_{n=2}^{\infty}\left(1-\frac{ 1 }{ n^2 }\right) \]

OpenStudy (anonymous):

I know I know but i need this: |dw:1417354343303:dw|

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