Respuesta :

mathmate
If n is an integer, then cos(n(2π))=1.

Take n=0, cos(2π)=cos(0)=1, n=1, cos(2π)=1, n=2, cos(2(2π))=cos(4π)=cos(0)=1...

If n is not an integer, well, ..... we don't know the value, which depends on the value of n.