Ths one has taken me like two hours to do with all the calculations.

Firstly we must establish something

Proof: By integration by Parts

Now if we define

Then

Now seeing that

Due to the overpowering effect of

And that

Then

So now we can get to the actual integral

My first intuition was to do as Krizalid said with the other and transform it into a function of cosines, but I found the working with the functions to be to cumbersome so I kept it as is and used the above knowledge to transform it as follows

Now noting that we are integrating over a rectangular region the ubiquitous Fubini's Theorem applies enabling us to switch the integration order scott free. Thus

Now here comes something horrible we must calculate

It took me an hour alone to do this calculation and it would take an eternity to type,so instead I will include the entire calculation of an integral of the same concept so those who read the others and did not see how to do it may follow along.

For the sake of alleviating calculations we know that

So by Integration by Parts

So if we expand this we get

Now you notice that if we add the last term and factor we get

So if you would actually do the calculation you would see that

And if you think that is bad you should have seen it prior to me letting my TI-89 clean it up for me.

So if we let

Then we can see that

From there we can see that

Due to the overpowering effects of

And

Then we see that

So now we must calculate

So if we look at them seperately we get

And similarly

So

So

So to match what Galactus's website said

Hope that was long enough for you . There has to be a better way to do it, yeah?