Thread: how do you do this integral

sin(wt)cos(nwt) dt

Originally Posted by richard7893

sin(wt)cos(nwt) dt

Make this integral into the form of udu and it integrates easily.

But if you do this your du=-nwsin(nwt). By doing this you cant substitute for sin(wt) because du=-nwsin(nwt)

Originally Posted by richard7893

But if you do this your du=-nwsin(nwt). By doing this you cant substitute for sin(wt) because du=-nwsin(nwt)

Ooops! Sorry I missed that. Eyes are wearing out from looking at the computer.

Hmmm, my first thought is to try the product to sum conversation for sin(a)cos(b), which looks like:



That should split up into things you can integrate separately easily.