Series question !
Study the nature and find the sum of the following series: \[\sum_{n=2}^{\infty}\ln(1-\frac{ 1 }{ n^2 })\]
\[S _{n}=\ln(\frac{ 3*8*15*...*n^2-1 }{ 4*9*16*...*n^2 })\]
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\[\sum_{n=2}^{\infty}\ln\left(1-\frac{ 1 }{ n^2 }\right) = \ln \prod_{n=2}^{\infty}\left(1-\frac{ 1 }{ n^2 }\right) \]
what's that pi sign never saw that It's the product ??????
its like sum sign
\[\prod_{n=1}^3 n = 1\times 2 \times 3\]
\[\prod_{n=1}^{10} n = 1\times 2 \times 3\times \cdots \times 10\]
so it's the equivalent of the sum sign for products
Exactly!
but how do you know that relationship ?
just expand it and see
o I saw it actually look at my first posts
we use below log property : \[ \ln(a) + \ln(b) + \ln(c) + \cdots = \ln(a\times b\times c\times \cdots )\]
sum of logs = log of products
\[\sum_{n=2}^{\infty}\ln\left(1-\frac{ 1 }{ n^2 }\right) = \ln \prod_{n=2}^{\infty}\left(1-\frac{ 1 }{ n^2 }\right) \]
I know I know but i need this: |dw:1417354343303:dw|
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