1) Complex numbers can be represented as ordered pairs of real numbers on a 2D plane, with the x-axis representing the in-phase (I) component and the y-axis representing the quadrature (Q) component. 2) A complex sinusoid rotating on this plane at an angular velocity of 2F represents a signal with frequency F, where F is the rate of change of the signal's phase over time. 3) Such a complex sinusoid can be decomposed into its I and Q components, which are real sinusoids 90 degrees out of phase with each other, with the I component in phase with cosine.