Angular frequency is defined as (2)(pi)(frequency) and can be calculated using the formula 1/square root(LC) at resonance frequency. The resonance frequency is an inherent property of the circuit, independent of whether a signal is present. In passive circuits, the input frequency remains unchanged, while the circuit can only affect the amplitude of the signal. When multiple frequencies are present, the passive circuit can selectively attenuate frequencies, favoring those near its resonance frequency. Therefore, the equation for angular frequency is applicable primarily at resonance.