This Question asks for the summation of the series below, through some use of derivatives and log
$$\sum_{r=1}^\infty \frac{1}{\theta^2 - (rπ)^2} = \frac{1}{\theta^2 - π^2} + \frac{1}{\theta^2 - 2^2π^2} +\frac{1}{\theta^2 - 3^2π^2} + .....\infty$$
Now , if you take the summation as Y then $$ Y = \frac{1}{2π\theta}\sum_{r=1}^\infty \frac{d}{dr}\log\frac{\theta + rπ}{\theta - rπ}$$ But I can't get ahead after this, so I need help