To begin, we must first understand what sinusoidal signals are. Sinusoidal signals can be represented as

where A is the amplitude, ω is the frequency in radians per second, and θ is the phase angle in degrees(phase shift). We can return to the sinusoidal signal by taking the real part of Euler’s formula:

For the moment, consider single-frequency circuits. Every steady state current and voltage will have the same basic form: