■ある無限級数(その163)
1/(1^2+a^2) + 1/(3^2+ a^2) + 1/(5^2+ a^2) + ・・
=(π/(4a))・(e^(aπ)-1)/( e^(aπ)+1)
a=qi/pを代入すると
左辺=1/(1^2−q^2/p^2)+1/(3^2−q^2/p^2)+1/(5^2−q^2/p^2)+・・・
=1/(1^2−q^2/p^2)+1/(3^2−q^2/p^2)+1/(5^2−q^2/p^2)+・・・
=p/2q{{1/(1−q/p)−1/(1+q/p)}+{1/(3−q/p)−1/(3+q/p)}+{1/(5−q/p)−1/(5+q/p)}+・・・}
=p/2q{{1/(p−q)/p)−1/((p+q)/p)}+{1/(3p−q)/p)−1/(3p+q)/p)}+{1/(5p−q)/p)−1/(5p+q)/p)}+・・・}
=p^2/2q{{1/(p−q)−1/(p+q)}+{1/(3p−q)−1/(3p+q)}+{1/(5p−q)−1/(5p+q)}+・・・}
右辺=(π/(4a))・(e^(aπ)-1)/( e^(aπ)+1)
=|πp/4q・tan(qπ/2p)|
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[1]p=4,q=3
左辺=16/6{{1/1−1/7}+{1/9−1/15}+{1/17−1/23}+・・・}
右辺=π/3・tan(3π/8)
B=1/1−1/7+1/9−1/15+1/17−1/23+・・・
=π/8・tan(3π/8)
[2]p=4,q=1
左辺=8{{1/3−1/5}+{1/11−1/13}+{1/19−1/21}+・・・}
右辺=π・tan(π/8)
C=1/3−1/5+1/11−1/13+1/19−1/21+・・・
=π/8・tan(π/8)
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