Intragral from 0 to 2pi e^cos(theta)8cos(ntheta-sine(theta)dtheta=2pi/n! where n=1,2,....

I got that cos(n(theta)-sin(theta))=e^i(ntheta-sin(theta))+e^-i(ntheta-sin(theta))

and now i don't know where to go from there?