Skip to main content

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

Required fields*

12
  • 1
    $\begingroup$ In case it helps, Maxima gives 2*%pi/b * (2*sqrt(1-b^2)+b^2-2)/(sqrt(1-b^2)+b^2-1). When computing with +i instead of -i in the exponential, it gives instead 2*%pi/b * (sqrt(1-b^2)-1)/sqrt(1-b^2), but it's actually the same. $\endgroup$ Commented May 19, 2014 at 10:36
  • $\begingroup$ Have a play with this Manipulate to see the dependence on b of the singularities of the integrand in the complex Theta plane: Manipulate[ContourPlot[Abs[Exp[-I Theta]/(1 + b Cos[Theta]) /. {Theta -> ThetaR + I ThetaI}], {ThetaR, -1, 2 Pi + 1}, {ThetaI, -Pi - 1, Pi + 1}, PlotRange -> {Automatic, 30}, Contours -> 50, Epilog -> {Red, Thick, Line[{{0, 0}, {2 Pi, 0}}]}], {{b, 0.5}, -1, 1}]. You need to ensure that the path of integration goes appropriately around the singularities in order to get the intended result. $\endgroup$ Commented May 19, 2014 at 11:07
  • 1
    $\begingroup$ My Series approach is offered only as a way of helping Mathematica to compute the answer that you seek. As for the complex roots problem, I don't have any inside knowledge about how Mathematica does its integrations or how it handles singularities that may (or may not) be important. See the answer from @artes below for more details on this, where I agree with the statement that this is all due to "imperfectness of symbolic integration". When there are singularities lurking around, you have to appeal to the underlying physics (or whatever) of the problem to decide how to handle them. $\endgroup$ Commented May 19, 2014 at 13:40
  • 5
    $\begingroup$ This appears to be due to a problem deep in Limit. Will try to sort it out (usual caveat: roughly even odds it sorts me out instead). $\endgroup$ Commented May 22, 2014 at 15:52
  • 1
    $\begingroup$ the bug is still present in MMA 11.2.0... Huh $\endgroup$ Commented Sep 19, 2017 at 15:36