This video demonstrates how to derive the frequency of oscillations for a 3-point oscillator system, in the specific case of Colpitts oscillator. A method is used that assumes that oscillations exist. Then, KCL for two nodes is written and a single complex expression is derived that depends only on a single non-zero voltage. We are allowed to divide all terms of the expression with this voltage and we are left with a complex expression that includes only the parameters of the system. For this complex expression to equal zero, we need that its both real and imaginary parts are zero. By equating the imaginary part to zero, we derive the frequency of oscillations.