Any hints for this one please?

$$\int_{-\pi/2}^{\pi/2}\frac{1}{1+2009^x}\frac{\sin(2010x)}{\sin(2010x)+\cos(2010x)}\,\mathrm{d}x $$

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    $\begingroup$ I tried that but it's not helping very much.. $\endgroup$ – Superbus Mar 24 '14 at 13:47
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    $\begingroup$ The integrand function is NOT integrable in a neighbourhood of a point $x$ for which $\sin(2010 x)+\cos(2010 x)$ vanishes. $\endgroup$ – Jack D'Aurizio Mar 27 '14 at 18:04
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    $\begingroup$ What is the source of this problem? The use of years ($2009, 2010$) is highly suggestive that this is from a college math competition. I have checked Putnam 2008-2011; this does not appear there. $\endgroup$ – MCT Mar 30 '14 at 2:18
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    $\begingroup$ Source: near the bottom of physicsforums.com/showpost.php?p=3433157&postcount=272 $\endgroup$ – user85798 Mar 31 '14 at 7:31
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    $\begingroup$ @JackD'Aurizio And aren't there a infinitely many of those points? It would seem this integral is "duly divergent"… $\endgroup$ – Geremia Apr 2 '14 at 2:18

To expand on the comment of @Jack D'Aurizio: when does $$ \sin \left( k x \right) + \cos \left( k x \right) = 0? $$

Examine the plot for the case when $k=1$.


Given integer $j$, the roots are $$ x_{-} = \frac{-\frac{\pi}{4} + 2j \pi}{k}, \qquad x_{+} = \frac{\frac{3\pi}{4} + 2j \pi}{k} $$

Over the domain, there $2010$ roots for $x_{-}$ and another $2010$ roots for $x_{+}$.

The figure below zooms in on one of these $4020$ singularities.



Integral is not defined.


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