Integrating by parts (how do you take care of problems w/ (e^x) and a trig function?)?

Hi pLaSmA, look at the factors. They are e^-y and cosy. What are the facts behind these? As we integrate e^-y we get same as e^-y of course with negative sign. And differentiating cos y twice we get cosy, same way with a negative sign. So we get back the same format as we do the integration by parts. So collecting that format on the same side we can easily get the value. That procedure has been done by our friends in detailed manner. Hope by this time you might have understood it.