- #1
opticaltempest
- 135
- 0
I am given the following series and its sum
[tex]
\sum\limits_{n = 1}^\infty {\frac{1}{{\left( {2n - 1} \right)^2 }}} = \frac{{\pi ^2 }}{8}
[/tex]
I need to find the sum of this series
[tex]
\sum\limits_{n = 3}^\infty {\frac{1}{{\left( {2n - 1} \right)^2 }}}
[/tex]
Is the method I used below this the correct approach? Is there a better or different way?
From the first series where n=1 we have,
[tex]
a_n = \frac{1}{{\left( {2n - 1} \right)^2 }}
[/tex]
[tex]
= {\rm{\{ 1, 1/9, 1/25, }}...{\rm{\} }}
[/tex]
Therefore I concluded that we can subtract off the first two terms of
the above sequence to get the sum when n starts at 3. Hence,
[tex]
\sum\limits_{n = 3}^\infty {\frac{1}{{\left( {2n - 1} \right)^2 }}} = \frac{{\pi ^2 }}{8} - 1 - \frac{1}{9}
[/tex]
[tex]
\sum\limits_{n = 1}^\infty {\frac{1}{{\left( {2n - 1} \right)^2 }}} = \frac{{\pi ^2 }}{8}
[/tex]
I need to find the sum of this series
[tex]
\sum\limits_{n = 3}^\infty {\frac{1}{{\left( {2n - 1} \right)^2 }}}
[/tex]
Is the method I used below this the correct approach? Is there a better or different way?
From the first series where n=1 we have,
[tex]
a_n = \frac{1}{{\left( {2n - 1} \right)^2 }}
[/tex]
[tex]
= {\rm{\{ 1, 1/9, 1/25, }}...{\rm{\} }}
[/tex]
Therefore I concluded that we can subtract off the first two terms of
the above sequence to get the sum when n starts at 3. Hence,
[tex]
\sum\limits_{n = 3}^\infty {\frac{1}{{\left( {2n - 1} \right)^2 }}} = \frac{{\pi ^2 }}{8} - 1 - \frac{1}{9}
[/tex]