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> An object is placed on a frictionless table with its one end attached to a cord which is connected to a pulley and the tension is maintained constant at 25 N. what is the change in kinetic energy of the object from its position 3m away to 1m away from the raised platform? 
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![poorly drawn, so not at all to scale...just shows the setup.](https://i.stack.imgur.com/EDPcw.jpg)

I think that we should integrate work with respect to theta here, over the interval $\tan^{-1}(1.2/3)$ to $\tan^{-1}(1.2/1)$. But for that, we need to differentiate work with respect to $\theta$, right? So doesn't it end up the same if I differentiate it and then integrate it? Or do I integrate the expression $F s \cos(\theta)$ with $\mathrm{d}\theta$ without differentiating it first?