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Student Support Forum: 'Mathematica gives inconsintent answers.' topicStudent Support Forum > General > "Mathematica gives inconsintent answers."

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Daniel Krawisz
11/23/08 11:18pm

Hi, I'm using Mathematica 6.0.0 for students.

When I do
Sum[Sin[n Pi /2]^2 / n, {n, Infinity}]
I get
(EulerGamma + Log[2])/2
and when I apply N to that I get 0.635181 .
Meanwhile, if I do
Sum[Sin[n Pi /2]^2 / n, {n, Infinity}]
I get 3.66547 .
However, it is clear that the correct answer ought to be infinity. When n is even,
Sin[n Pi /2]
is zero. When n is odd, Sin[n Pi / 2] is 1. Hence the sum just amounts to
Sum[1/n,{n,1,Infinity,2}]
Which does not converge. What's going on here?

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Subject (listing for 'Mathematica gives inconsintent answers.')
Author Date Posted
Mathematica gives inconsintent answers. Daniel Krawisz 11/23/08 11:18pm
Re: Mathematica gives inconsintent answers. Kaveh 11/25/08 9:54pm
Re: Mathematica gives inconsintent answers. yehuda ben-s... 11/27/08 04:55am
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