Hey /sci/ so I read this explanation about why a capactior (or inductor) is a linear device. Well I know it is linear since it obeys the ohm's law. But this particular reasoning kinda threw me off. It was based on the fact that taking derivative is a linear operation so, for example, Ldi/dt is by definition a linear dependency. But doesn't that depend on the input signal? in other words the function being differentiated? Of course sin'(x) becomes cos(x) which is sin(x+90) so you can argue that the signal waveform is preserved and only the phase has changed. But what if we forget about electronics, and the function is ,say, a cubic polynomial?? Differentiating will result in a quadratic polynomial. Which would mean differentiation is not linear?? My thinking is probably wrong but I am lost. Where am I wrong?