Trignometric Polynomial complex form

by phillyj
Tags: complex, fourier transform
 Mentor P: 18,019 Substitute $$\cos(nx)=\frac{e^{inx}+e^{-inx}}{2}, ~\sin(nx)=\frac{e^{inx}-e^{-inx}}{2i}$$ in the series and rearrange everything. This should give you the required form.