518 Armmtlix A Solutions to the b:xPrcisrs r[k] 277 ' = [I;] t h) when k = - T X(c'") = X,,(jw) mit R = wT Note: Even wheii e j n ternis not, appear iii t,lie result, the spectrum of a serics usually i s written x ( e j ' ) c) Fourier series X(e.irz) A I L ~ J y l b / "with * = I" f uiidanieiital period