I have such a question: if on RLC circuit, initial conditions are not set to zero, I mean, if capacitor, for example, has some initial charge, then superposition method cannot be applied to the circuit because it is no longer linear, right? I simulated it in PROTEUS, and got correct results (see attached pic.). And now, on page 667 of "Foundations of Analog and Digital Electronic Circuits" by Anant Agarwal, he uses superposition to solve RLC circuit with initial conditions..... can anyone please tell me whats's wrong?