using FT of a Exponential continuous to discontinuous∑akejkw0t↔F∑2πakδ(ω−kω0)\sum a_ke^{jkw_0t} \xleftrightarrow{F} \sum 2\pi a_k \delta(\omega - k\omega_0)∑akejkw0tF∑2πakδ(ω−kω0)
