ABSTRACT
This chapter provides a review of complex numbers. If one is multiplying or dividing complex numbers one will prefer to use the polar form. If one is adding or subtracting complex numbers, one will rather use the rectangular form. The reason for that is the ease each form provides in the corresponding calculation. When one adds two complex numbers, one adds their real parts and their imaginary parts separately to form the addition. When one subtracts two complex numbers, one subtracts their real parts and their imaginary parts to form the subtraction. To divide two complex numbers, one divides their magnitudes and subtracts their phase angles. The chapter discusses Fourier series, sin-cos notation, Fourier series approximation and the resulting error. It also discusses the Theorem of Parseval, and systems with periodic inputs.
